Please help me with my the plants in my garden

Sorry to put this in English, my Dutch is not so good. Hope somebody may help me and give some tips.

I have some plants in my garden recently the leaves has been eaten by unknown bugs(I think).

Anybody can help me to figure out what kind of things I can do to prevent the plant been totally destroy? Thanks a lot. I really don't know much about the garden and plants, and willing to learn some. :).