How easy is learning a foreign language as an adult?
It’s not about how old you are, it’s about how interested and motivated you are. I started learning Spanish at 30 because I had no choice and a couple of years later I was fluent. I had to use it every day and this is what makes the difference. You must do something every day, whether it’s repeating something old, learning some new stuff, reading a bit of a newspaper, learning a song, etc. Practice makes the difference. Grammar alone is helpful but almost useless when it comes to using the language.