掲示板 Forums - Japanese learning

I don't know if my info will be helpful since I use both books and the app to learn as well as learning from school but from renshuu,

I have developed more vocabulary and kanji as well as some grammar structures and casual form speech from renshuu alone.

However, I have had books and education through school as a foundation (particularly hiragana and katakana) so since you said '(without book)' that is the best I can offer in terms of my experience with Japanese as someone who uses more than renshuu to learn.

From my perspective, I had to use more than just online resources and apps to get even close to halfway through the N5 content not knowing much grammar or learnt to listen yet (renshuu does not offer listening as far as I have searched)

I hope this helps and good luck with your research

Edit: Also exposure to things such as anime, manga, music or any Japanese media helps lots too.

Also very sorry for the late responce. I hope you can still make the deadline.