Ask HN: How do I learn a new language in my thirties

As someone who is learning a new language (German) in early thirties, I find it not as easy as when I was learning English as a little kid (Sinhala is my mother tongue)

Specially with the pronunciation. For the love of god, I cannot differentiate the pronunciation difference between letter u and ü. As an example musst and müsst both sounds the same to me. Maybe this is because I'm too old. Has anyone else experienced the same? If so how did you overcome it?