First, there should be a valve under the seat to adjust the pressure for the three point hitch. Check your operators manual.
Secondly, have a look at this thread for some information.
https://www.tractorforum.com/threads/kubota-hydraulic-problem-solved.12156/

 

Firstly I know about the valve. But something I didn`t point out is that when I got it worked fine
but I left it parked for one or two months and when I tried to use it again the moment it reached max height with a rotovator attached, it slowly went down and never came up.

 

Hi Peter, in case you never got the manual, here's a copy.
https://www.icloud.com/iclouddrive/0lbQ9eRl8Xs2DqHLkE6Cy33wg#L245DT_Service

 

Ebay usually has a good selection of shop/repair manuals. Some downloads.

 

Kubotabooks.org (I think that is the web address).

 

This Complete Kubota L245DT Tractor Service Repair Manual includes needed instructions to maintain, service and restore your Kubota L245-DT tractor using unique diagrams and producers specifications. Kubota L245DT Tractor Service Repair Manual

 

Kubota L245DT Tractor Service Repair Manual