Couple of Questions about a 3511

Hello,
I've just purchased a 3511, and I have a few questions about it, as I've never owned a tractor before, but have some mechanical experience.
Firstly, the hydraulics aren't working. They stopped suddenly, as they were working fine last week. Does anyone why this may have happened? And where can I check the hydraulic oil?
Also, I have no clue what all the levers below the seat do. Again, does anyone know what these do? ???

That's about it for now, but I'm sure there'll be more in the future, looking forward to helping, and being helped!

Hi
To anser your qustions i vil start vhit the small lever to the left inn front off your seat, it coples PTO and hydrolic pump, all the way dovn or forward is hydrolic only one step upp is pto and hydrolic one more step upp neutral and all the way back or upp gearedependet pto. The right one is hi and low range gears. Gearebox oil is used for the hydrolic you chek it vhit the dipstik on righthand side off gearebox cover.

Bjarne,
thank you very much for taking the time to respond to my questions, as it is very appreciated.