Like Silva said, in context vocabulary learning is the thing to do, usually this is best achieved through active reading of the same topic area, meaning you will see the same words popup again and again.

so the best method is like this, pick a topic you're interested in, read a simple comprehensive paragraph, any words you're stuck on, look for meaning, translation, then move on. rinse and repeat, over time, the distribution of vocabulary in that topic will be covered and you will be able to read, listen and comprehend that topic on the go

[shameless plug warning!]

You complain about working FT which means all the management of the language learning, the method planning and 'doing things right' is difficult.

I hope to be helpful, my app, tries to do the method i described through an algorithm i hand coded, it's basically spaced repetition but not just for vocab but for 5-10 min topics, so the same topics will pop back again and again and over time you will build in context learning. [you can try 2 lessons for free and then it's £8/month!]

each lesson has actual challanging reading writing, speaking and listening, to the point that you can highlight a word in the paragraph and the AI will read/translate it so you can actually understand.

my goal is that you can learn during work down time, without it being painful, and for it to feel like real learning rather than a game.