Calisthenics Unity

Hello!
I can hold front level for about 3seconds and the slowly fall off, i think the problem is my lower back, or like i'm pretty sure it is :D
So, what are good exericses for training lower back? I have strong upperback, but i don't think i've ever trained lower back, only if lower back works in wide pullups etc then yes, but not like targeting lower back.
Thank you! :)

Lower back hyperextensions, lower back holds, lower back raises, I think dragon flies work the whole core (abs & lower back) as well. :)

Yep, as Gligor said, all those are good exercises. Also, lower back crunches and reverse plank are great exercises for the lower back as well!