I was able to 1* the 7th map but near the end my team got completely wiped out, luckily I had killed enough units to make it through with a bit of life left.
Map 8 on the other hand, I need to 2 star that one to reach 21, that is where I need to mold and lvl my team to accommodate that map. Until then I am happily farming silvers, just hope the drop rate doesn't get the best of me in the end.