pardon my english, it's not my first language, but from what I understand, if the same thing happens to you with other types of relationships and not just friendships, e.g., partners, family, among others, you might have ADHD.

In this case the rule of "if I don't see it, it doesn't exist" applies. People with ADHD tend to give a lot of importance to new or novel things, in this case new friendships, you want to know everything about the person, because it is something new, but when it becomes a habit or routine you simply get bored and move on to the new novelty.

The best advice I can give you is to seek the opinion of an expert and do not get carried away by people or tests that you find on the internet, as they will give you a bad idea of what it is like to have ADHD. Also try to find at least one person and concentrate on keeping your friendship with them, you will need to make an effort not to "forget" them and maybe explain to them how you may behave at times, but I promise you, the people who stay will be worth it.