Which exercises not to do, to avoid lower back strain?

Hey people!

As yours, my life has improved so much since I started using fitness blender, a thanks to Kelly and Daniel :)

Also, as many of you, I have a sedentary job, and often my lower back feels a pain or strain. I have started strengthening my abdominal muscles, just so they can better support the back, and I don't go too low when doing plank exercises.

Are there any exercises that are big No No, just so I can improve this?

Thanks guys!