5. g6 that is true but also not true , first bishop on b2 will not do much cos that diagonal is closed , he will have to open with d5 push, also ( for me , i play queen gambit ) best way to couter it is some type of tarrasch defence . Also N on f3 is blocking ur peons and you will lose time cos of that. Some players prefer to as u said go for Bd6 but with c5 or c6 first so u can then after c5 ( from white ) move to c7 and have nice diagonal . This is all about queen gambit and if he didnt see that opening before the played great !
14. Black is now in problems cos he didnt respond the best at the opening, Bb7 is closed , c7 will be the main problem soon , and he made a good exchange of white bishops +
15. c5 is nice try but quick solutions to the problems are not good in most cases , after exchange central peons are very weak and they are target for white
17. white has stoped black peons from advancing and he will put pressure them
25. again he is trying to solve problems in the quick way
Your kid played great ! vs much better oponent , the biggest mistake a seen is that he was not prepared for this opening and nothing else, mb u shuld post if u have his game as white
I would say that he does not have a tactical problesm as u may see on move 50. where he does not take N cos then he cant prevent peon from queening, most of the problems are long term strategic
