Kickaha has offered lots of detailed comments about tactical issues in his review.
The only feedback I have to add is about the opening.
White appeared to follow the basic strategy of âcorners first then sides then centreâ, but in fact just placing one stone at each of those places is not enough. One stone doesnât âdoâ (secure) the corner, so itâs not time for the sides till there are more in the corners.
This is why at move 18 the AI says the game is 80% in blacks favour. At that time, white has stones at each star point, apparently âclaimingâ at least half the board (plus komi) but in fact white has zero territorty at this time. Zero. In contrast black has solid two half sides and solid influence over their side of the board.
From here, if black chose, they could invade almost anywhere on the left side of the board and live. That means white has no secured territory.
At move 5 white should still have been focused on âCorners firstâ. This means that the move choices were probably C15 D15 Q15 R15.
Because white is âfollowingâ black, getting into a building a framework race is not a good idea - instead white needs to mess up blackâs framework from ever getting started. This leads us pretty much to Q15.
From there the game would have been totally different 
I have one very important thing to say about this game.
At the end of the game, White resigned.
This was a mistake.
You should just click on the âpassâ button. Black will pass too. Then the game will go to the scoring phase and you will know the exact score.
The board is roughly cut into two halves, and there is no reason to resign at this point. Just pass and count the territories. Whoever has more territory wins.
In fact, unless you are extremely proficient at counting, and are 100% confident that Black has more territory than White, then resigning is a mistake.
Besides, even if White loses, itâs still better to pass than to resign. The game will go to the scoring phase and you will know the exact score. You will be able to see how much territory White has made in their area, and how much territory Black has made, and this is important information to develop intuition about how much territory there is on an area on the board.
Full versus empty triangle
In figure 1 @kickaha refers to the marked stones as an empty triangle, which is an inefficient shape. K4 is too close to the two other white stones. It would have been better placed at H4.
Figure 1: Empty triangle
Triangles are not per se inefficient shapes. In some cases they are efficient. In figure 2 a white stone at J16 would have saved the white player a lot of troubles. This is a nice example of a full triangle.
Figure 2: Full triagle
Moral of this: triangles are not bad by definition. It depends on the context. So before creating a triangle, try to ascertain if it is full or empty.
Full triangle: good.
Empty triangle: bad.
Apart from the guzumi! 
Would be nice to stay on topic, giving advices to low DDK and not overflowing them with guzumi and such.
In 99% of cases an empty triangle is an inefficient move and a bad shape. Enough.
This is another way to consider the inefficiency of an empty triangle.
Group A has 1 liberty less as group B (but the same quantity of stones)
Exageration can help too.
Group C has 2 liberties less as group D.
Now anyone should restrain himself to not come and say that sometimes group C is a good shape: itâs just completly out of the subject (for a review aimed at DDKs)
I agree in principle with simplifying advice to low DDK players, too, but I also feel an important aspect of Go is that no move is âalwaysâ 100% âbadâ and there is always context to be considered in all situations.
In terms of local shape, I might say the guzumi (good empty triangle) appears at least 3-5% or more of the time in relatively common âgoodâ opening/midgame/fighting shapes like the 3-3 invasion to a 4-4 corner enclosure here: ![[Diagram]](https://senseis.xmp.net/diagrams/33/1c04b12c7b5776e5234215dc92fc0103.png)
I know that as an inquisitive beginner I often had questions like: "But surely it isnât always bad to play this shape, is it?', and I found explanations to the effect that âX is always badâ a bit confusing and stymying for the curiosity, especially when I encountered excceptions to it.
Sometimes Iâve found that learning general Go âprinciplesâ as if they are set in stone without exception can be more confusing than helpful.
So it was posted in the hopes that it may aid either the OP/thread readers or those reading this thread in future in seeing situations in Go with some flexibility, as contextual, even if they are just a beginner/DDK. ^^
i agree on that aspect of exceptions but i just usually put it as a general aspect and avoid to distract.
i put that even more caricatural example with 4 stones groups because if you want here to show why it could be a good move, you gonna have a big chance they just give up playing go !
To come back to the review, i would really like to talk a bit more about this empty triangle here
Till this move was played, i would say the quality of the game is pretty high, looks like high kyu players or even dan maybe.
It should be made clear that this move ruins all but no worry there are in it many common mistakes it may be interesting to develop.
So thirst is as said an heavy shape called empty triangle. When adding a stone here it has very low usefulness. It doesnât help very well to make eyes. It doesnât attack black.
I would even say more .Itâs an invitation to black to attack the white group.
Just imagine a black stone now between the clumsy 3 stones and the corner stone. Ok?
When playing in this lower side, itâs good to try to anticipate a black invasion, and prepare to counter: that can be a step forward into the center, an extension on the edge to give more life or an extension from the corner stones to help the 2 white stones from far. That can be even more subtle like playing somewhere else.
In fact there are more as 1 bad feeling in this move instead (sadly) like donât play near the strength, donât just follow your opponent, treat heavy stones or forcing moves lightly, try to have multiple direction in each of your movesâŚ
This awful move is a treasure for improvement.
Edit: still a bit more for the middle game.
I guess the cut by black at J16 was something important for both players minds and that was justified and not easy to predict the outcome.
Now it seems that you didnât care (or even see ?) that you got all your wall surrounded by black. Not really a cool result, so you may think of other moves there to play.
Ahah, makes sense!
I admit I had an unusual level of interest and curiosity about such things even as a DDK but that they can be distracting and complicated to explain ! ^^
As Groin and kickaha pointed out, the cut at J16 was a major key point for both sides, and protecting it (J16 instead of L15) was a really big key point.
Itâs also worth noting that this type of connection at L15 in response to K14 creates 2 empty triangles!
So itâs worth considering alternate moves in this type of shape. If the L15 cut is the most important area to protect, often a move like K15 or L14âor even indirect defences of the cut by strengthening nearby shape, such as J16 or J15âare typically the best move to play locally, and far more efficient.
K15 or L14 would tie up one liberty on K14, and form better shape facing the outside (a 2-stone wall), and moves like J16 or J15 strengthen the J16 cut, making it indirectly difficult for Black to cut at L15, and build some influence/thickness towards the upper side and centre.
(Although sometimes L15 might be best due to shortage of liberty issues, the double empty triangle tends to be a very inefficient shape in fighting and played only when other moves donât work.
By itself, L15 does little else on the whole board other than connecting the K16 and M14 groups, and it also removes a potentially useful open liberty at L15.)