I used Anki for learning Chinese and visiting the country.

Now I'm using a relatively new app called LingoDeer to supplement my Korean learning while also being in Korea

I'd say I like Lingodeer more than Duolingo / Memrise which didn't feel effective for real life situations since you could essentially go through the two apps without feeling the need to apply what you've learned.

Anki is more independent learning which is excellent for getting vocabulary down in my opinion.

Yes, fully immerse yourself by moving somewhere where the language you are interested in learning is spoken.

Or use Anki, but full immersion seems to work better.

Babbel is pretty good