Thanks for your comments.
I'm aware of a couple of parallel 5th's. But somehow they are a little bit justified by the voice leading, I think. (that doesn't mean the are "good", but it gives the reason why they are there)
The changes I would need to make in order to fix them are quite big (I think), so I'm scared to change it. (m. 7-8 and 25-28)
I have posted a new version with less parallel 5th's and 8ves. (only 7-8 and 25-28, has stayed, I guess) Especially the modification in m. 9 sounds weird to me, but I have heard the previous version a 1000 times so probably it's just me.
Are there other parallel 5th's or 8ves?
What do you mean exactly with "the first page is still promising"? (I probably don't get it because English isn't my native language)
string quartet in g less parallel 5-8.sib
string quartet in g less parallel 5-8 (sib 2).sib
string quartet in g less parallel 5-8.pdf
string quartet in g less parallel 5-8.mid