How do you manage learning so many tenses?

Practice suing those tenses in speech and writing when you can. If you get it wrong, don't worry! As long as you keep practising using those tenses, you'll be confident in using and manipulating those tenses quite easily like you do in English. It's okay if it takes a while for you to get a hang on them. As long as you practice them regularly, you'll get better before you know it.