I will tell you how I teach languages to my child:

Monday, Tuesday and Wednesday we learn French
Thursday, Friday and Saturday we learn English.
Sunday is a purely Polish day.

What do I do?

I read foreign books for goodnight, before putting him to bed.
I let him listen to foreign songs.
I let him watch foreign children films.
I play with him with his bath rubbers toys, speak to him in a foreign language, and I show him stickers on the bathroom wall, during his evening bath.
I let him listen to foreign audio stories.
I play games (using the body, fingers, singing songs with actions) with my child