Simple Grammar: present tense + DEPUIS
Sometimes English grammar is more complicated than French grammar!
To talk about how long you have been doing something in French, you just need to use the present tense + DEPUIS
NOTE: depuis can mean FOR or SINCE
I have been living in Oxford for 5 years
J’habite à Oxford depuis 5 ans
I have been learning French since 2018.
J’apprends le français depuis 2018.