Calculation for Hydraulic system

Hello Please see the schematic in attachment, we have give you the data we have. We need complete calculation in excel(or same ales) document, see we can change the parameters as we like and get results so all calculation need to be connected!! Q3,P3,P4 are constant and you do not change them!! You can change P1,Q1, P1 cannot be bigger than 15 bars and Q1 cannot be bigger then 15 l/min H1, D1 need the smallest possible!! For P4 i am not so shore it is ok( this is mechanism for reverse osmosis system) and P4 is reverse water used for recover energy!! Q2 is pure water and it is around 10% of intake sea water and 90% is P4!! For P4 you need to fined is it 30 bars or not!!