Here is some information about the GRP barrel:
The sloping bottom container mod  is required, this will be downloaded automatically when you have selected the mod and started the Savgame.
Why is this needed?
Because this can be coupled to the trailer and thus filled and operated.
You can either put it on with the front loader or drive next to it and hitch the R button. Just like it is with the sloping bottom containers.
Before filling, the barrel must be opened the gap otherwise no filling is possible. All functions are also listed in the Help menu.
Here is also the link to the mod: sloping bottom container mod
There are two version one under animal husbandry for all sorts of liquids.
And one under liquid manure tanks with this you can drive liquid manure but only has a working width of 2.4 meters.
Price: €18,551
Category : animal husbandry
Category : slurry tankers
Capacity : 10000 L
Thanks to Henrik for building the barrel and approving it
Thanks to Glumpii who made the decals.