The Einsteins of Bonsai
Pardon my french but you will always have 'smart asses' in every hobby as with Bonsai. They might seem to know everything and you might use their knowledge in vain. I have also noticed that many controversial things are written or told about bonsai keeping. Also on forums you will hear one claim this and the other the opposite. So sometimes you have to trust your own gut feeling. Keeping your bonsai healthy is not as obvious as it seems. Learn but try to follow your own good sense is my advise.
Adding personal character
Some ambassadors such as Walter Pall, an Austrian 'rock' in the world of Bonsai, will criticise the current Japanese style of (over)shaping their trees and finds them to commercial. I can relate to his view and prefer a tree that resembles the real thing in nature rather than a meticulously trimmed and shaped tree according to the 'rules of the art'. But this of course, has a lot to do with how you want your tree to look according to your personal character. And as with every artist you should try to integrate your soul in your trees.
Books and videos
There are very good books about the art of bonsai on the market. Sometimes it is more accessible to watch a movie about how to prune or repot a tree. There are quite a lot of informative videos available on Youtube about keeping Bonsai.
The best thing of course, is to join a bonsai club where you can exchange information and ideas with other members and where courses are given at the same time. This is where you will learn the most and realise that not only you make mistakes.
Protecting your Bonsai
Excessive exposure to sunlight can damage your trees. In the summer of 2020 it nearly ruined my collection. Especially the pine trees were badly affected and started to become brown and losing needles. Some might say that Japanese Pines need full sun exposure. I'm not so sure of this. They will survive in nature in full earth but in a pot is a different story. In very hot periods I now protect them from UV rays with a protecting sunshade and move some of them in a shady place. Also watering at least twice a day in such warm periods is recommended.