احسن الله اليكم If someone can usually understand more than 50% of the duroos in Arabic, but he isn’t ready for taking notes in Arabic. Is it wise to focus only in Arabic lessons and struggle in taking Arabic notes, and sometimes in another language, or to also have English lessons ?

Ustadh AbdulAziz al-Haqqan

Seek ilm in both so that u don't lose out on ilm and u can still increase your Arabic, unless you're increasing your Arabic level through other studies.