What size pipe is it? Looks kind of small for a long run like that.

2" is fine as long as you get that dip out of it. Ideally you want to see a 1/4" per foot slope in your drain pipes.

1/4" per foot minimum for < 2.5" diameter pipe. But note you could slope too much and the liquids may outrun the solids and cause clogs like you're seeing in your pipes. But that is controversial and most codes got rid of max. slope.