Hi there! I’d be interested! Let me know

Beside means literally “next to”. “Besides” is generally in american usage, if I’m not mistaken, and just means “anyway” or “in addition” or sometimes a type of “it’s not really of importance” The keys are beside the phone. He can do a lot more besides. Besides, he didn’t like those jeans anyway

What does C2 mean to you? Many if not most native speakers are not C2 in a language. If that is your goal I would suggest reading a lot of books in your target language on different topics, and writing essays and having them corrected by qualified language teachers who teach the language to native speakers

Think of lembrar being more like the verb “to remind” so you have to remind somebody, in this case it is yourself. I remind myself being Eu me lembro

You should never use it as a non-native speaker. Just understand it. It simply means “isn’t”.

"adheres to" is the best choice in this situation. It means that it is a long held ideal/belief. Definitely the type of thing someone who likes to keep old traditions would do. "holds to" is more to do with justice as far as I can think. "Holds to account", "hold someone responsible" type of thing. It certainly doesn't work well in this context. "stands by" is more when something is challenged and you refuse to yield to the challenge. "I stand by my statement that the earth is flat!"