When I review there I see a problem first is my memory but I am going to skip that the second problem is even if a move Is a mistake I don’t know why it’s a mistake, can someone please advice me on this.
This is a difficult question that also has a rather complicated answer.
It’s easy to identify a mistake. You can analyze your game in a strong Go playing program and notice a sharp drop in win rate.
Knowing why a mistake is a mistake is the hardest part that involves understanding Go theory: thickness and thinness, how to judge positions, good and bad shape, to name a few. Frankly, many single digit kyu (SDK), dan and even professional level players struggle with understanding their mistakes consistently.
It is difficult, being at the level you are now (not just directed towards you, but the reader in general), to look back at a game you just played and say move X is a mistake because Y. While we may be able to do that to an extent by knowing move X didn’t steer the game in a way you wanted to. However, that usually isn’t sufficient to prevent us from making similar mistakes in future games. To do that, we must improve.
To improve is to be consistently exposed to new ideas. The reason why many people find teaching games very useful is that these new ‘ideas’ are most geared towards you. In other words, the stronger player can see weaknesses in your specific play style, and give you advice that addresses these problems specifically. For most of us, who have no regular contact with a strong player nearby, we can absorb new ideas from relevant Go material, whether these be books, magazines, reviews of others’ games, online videos, etc. But, these methods are generalized towards a wider audience, and it requires extra thinking to find some relevance in your own play.
After the AI breakthrough in 2016, we also have strong AIs at our disposal. There are many open sourced Go playing programs that can analyse our games. Though these programs can’t give us a verbal reason for a mistake, with sufficient background in basic Go theory you can explore new ideas through them. For example, you can compare and contrast the variations you played and the variations AI recommend to get an idea of what you’re doing wrong.
So, as you can see, the two questions you asked in the forum are actually interconnected with one another. 
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