Thanks for the quick replys. Since I am just starting to understand how OpenWrt works and I dont trust my skills with ssh so far, I think I will try something different.
But I found this PureFusion - wrt3200acm, wrt32x, wrt1200ac, wrt1900acs, wrt1900acV1, wrt1900acV2 Builds. It seems to work and has sqm already built in, if I am right.