I feel like past me wrote this post!
I felt exactly how you do only a month or so ago. I was great at remembering readings and individual words, but actually stringing things together using the grammar I learned was impossible. I think I’m on track to improving this, though. Here’s what I do…
Whenever I learn a new grammar point or “trick” through Genki or a friend, I then find multiple sentences and situations to use it in. Often I’ll just go through situations in my head and role play how the conversations would go.
After that, I try to create real sentences and post them to HelloTalk. You probably know, but HelloTalk is an app where you can post a message and others can read and correct it. It’s great for getting natural corrections. In my workflow, I think it is important to do this step quickly after the “role play”, because I don’t want to internalize something that is wrong.
I take the information I learn from the HelloTalk corrections and do the process again. Creating an imaginary situation, responding to myself (okay yeah, a lot of this is talking to myself), and then crafting sentences for HelloTalk.
So far it’s working for me. Instead of new grammar points just being textbook knowledge, I think I’m on track for internalizing proper use and appropriate situations.
I hope any bit of this will help you find what works best for you.