tldr; you need to read, listen, and learn words in your target language.
You can learn any language you want. You just (probably) aren't doing it right. Heres my two cents for those interested. Trust that if you follow these general ideas you can get good and have fun learning any language. These ideas are all based on the Input Hypothesis. From my time learning japanese spending the bulk of my time reading novels and watching shows has proven to be the most enjoyable and approachable way to learn the language. Literally you just need to sit down and read as much as you can and watch shows you like in your target language. Don't use subs or translate to your native language. You need to aquire what you are immersing in. I found that when I am reading really trying to disect the sentence and fully understand it has helped my language abilities the most. When I listen I will use japanese subs (my listening skills are poor). Try to focus on the content you are consuming and listen closely. If that is tiring just relaxing and picking up what you can could prove useful, but at the very least will improve your tolerance for the language.
Now why does this work and why should anyone listen to what I have to say? Besides the fact that it worked for me enough to get comfortable reading japanese in ~4 months, think about it like this. Did you study your current language to learn how to speak? Probably not. So why can't you do it for other languages? You can.
Screw grinding textbooks and doing stupid exercises. Just read and listen brah.