Constant knots in my line

Everytime I go fishing I have to finish early because my line becomes tangled beyond repair.

I have noticed that after about 1 hour of fishing my line becomes loose on the reel. And shortly after that it becomes tangled.

What are the possible reasons this could be happening?

I'm lure fishing. I'm using .25mm line, 3.2 inch soft lures with .07 oz jig heads.