Where do these strokes come from in Minecraft?

(ignores the black bar on the right) where do these lines come from between the blocks? I have that in FTB and normal minecraft no matter which version. Thank you

In the graphics settings somewhere, I also had times.

I do not understand what you mean. This will just break the blocks. The landscape consists of many individual blocks. That is normal

Do you happen to use Optifine?

No that is not normal that between the blocks small pixel lines are where you can see through

Ahh many thanks "somewhere" there are few more settings than one or two

Not on ftb but in normal mc yes