A young Yeshiva man asked me how he could possibly marry and live in Israel when his Hebrew was so weak. In fact, his proficiency at Hebrew was not bad, but it wasn’t “Israeli”.
I will repeat what I told him:
If you don’t live in Israel, simply learn Derech Hashem by Ramchal. Skip the quotes (made of different versions of Hebrew, etc.). Derech Hashem is better than Mesillas Yesharim, which has far more quotes. And you stay in the Beis Medrash.
For demotic, ethnic Hebrew, find certain kinds of speakers on Kol Halashon. I’m not going to mention specific names. Ask your Israeli friends.
Spend many, many hours on this.