I've been learning for my whole lifetime. But my English level is not expanding. I've remembered the 16 tenses formula over and over, I feel like "Ok, I understand and I can do it". But every time I wanna do writing, I keep confused which tenses I should use. Any tips how to learn grammar?

質問を翻訳

You won't get good at grammar by studying grammar rules. It is how they teach it in schools, but since when do schools do anything that makes sense?

To get good at grammar, you need to cultivate an intuitive feel for what sounds natural, and what doesn't. And that comes from having seen and heard a large number of examples.

I'm not sure what the level of your abilities is, but if you're at the point where you can watch videos or movies in English, without subtitles or with English ones, then doing just that is the best thing you can do to learn English. Find English videos on a topic that interests you, or put on some Netflix.

It can be hard at first. It's fine if you need to look stuff up every now and then. If it gets too exhausting, you can do things like, watch a few minutes with English subs, then switch to your native language for a while to rest and enjoy what you're watching. Or just go for something shorter.

The best thing about this is that it doesn't really feel like work, but subconsciously you'll be training your brain to know what's correct and what isn't, and choosing the tense will become second nature.

When I write in English, I don't even think "oh, to say this, I need to use the future perfect continuous tense, so that'd be...". This kind of knowledge is useful to verify that you're using the right tense when you're still learning, but the decision itself should be entirely intuitive. Drilling the rules will not make you move closer towards that goal.