At the Moment u have liquid manure.

This is where you can collect your liquid manure. It's along the back side of the barn between it and the pastures.
And the bottom line of the left column an the photo below is where you can see your fill level.

Hmm, yeah that is where im checking but it's always at 0%...
do you have Bulls in the barn 1-5 or only on the pasture?

I have more than i could ever use but i did Not Check If it increases in latest 0.5.x version.

Same here, i dont check this after the latest patch, but normaly pump up the Animal hall with bulls,
make a feeding task with a Helper every day, (you need to hire 1) you need enought silage at home,
how to do this is one of the first quests you learn after start playing Cattle & Crops, than jump forward in
time, normaly shoud work with sleeping at home in your house.
but you also can buy manure at the Biogas plant, its not that expensive, ant next to the biogas plant is another
place to buy manure, i just dont know the name now, an when you buy manure there you also earn Points there
what you need when you want to buy land from them.