Exhaust pipe bathroom possible without slope, commercial bathroom, insulation

Hello there first of all.
And actually I have the following question.
I’m currently setting up a business bathroom and unfortunately the whole thing has no window.
So now I have to rely on ventilation... where I was thinking of a humidity-controlled fan.
So far so good... yesterday I broke out the 100 hole from the partition wall from the bathroom to the garage and from there it should then go along the ceiling of the garage outside.
But now I have the following problem.
The hole came out exactly in front of 2 pipe lines running across the ceiling of the garage... that means I have to go directly after the wall with a 90-degree bend past the pipes and then 4m across the ceiling of the garage to the next wall. Since I also want to insulate the garage ceiling in summer because the kitchen is above, I didn’t want to run the exhaust pipe too deep.
Now the question is, do I have to plan a 4-5cm slope over these 4m or is it enough if I simply run vertically after the 90-degree bend and skip the slope?
Because the shower is only used once a day, so not much condensation can form, right?

Regards David