How long do you keep your lessons?
I like to study a lesson once, and then add all of the lingqs to anki to actually remember them. Then i listen to the audios a certain number of times, if i was brand new and the audios were short honestly maybe 25-30 times, when i started lingq my portuguese was already ok so i listened 15 times. By the time i got to advanced i listened 10 times. And now i consider myself pretty fluent and i listen 5 times mainly passively.
I keep all my lessons that has a yellow word, just for comprehension purpouses. I keep reading new content, but once in a while I read the old ones to improve my comprehension on reading and listening. Once I already know the content, I am able to train my brain to think in the speed things are happening. Surely I take this time to review the old vocab.
I'm studying Spanish as well and tbh, I remove lessons from my feed almost as soon as I'm done with them. I know some people like to reread lessons, but I never do because I find it pretty boring. When you remove lessons, you don't lose any stats or lingqs. So there's no real harm in removing a lesson and moving on to the next one. If I were you, I wouldn't worry about forgetting / remembering vocab, you'll do both naturally and it'll feel mostly random. Sometimes I see a word or phrase so often and I think I've got it memorized, so I un-lingq it and then days later I can't remember the meaning anymore and I have to re-lingq it. Forgetting is part of the process.
By reading a lot of different material though and in the process, exposing yourself to hundreds of new words, forgetting a few isn't a big deal. Aiming for perfect memorization on every lesson may not get you as far as you want as quickly.