Also I would like to say that during last 4 or 5 years something has become my main goal (at work). I do not know how which preposition is the correct one, whether to use "the" with "last years" and if "get" can be used for the change or something else describing slow change.
During (in) last (the) 4-5 years, it got (became? grown?) my main
goal.
Best Answer
You could also use "Over the last five years". I would also consider "primary aim" as an alternative to "main goal".
If you'd like to say 4-5 years, I'd use "In the last four to five years". You can also swap the clauses if you like to: