Synology permissions for web folder and site folders

I am having trouble with permissions.

I am using synology ds411+ with virtual hosting setup

I have a folder for websites volume1/web
The sites are in
volume1/web/site1.....
volume1/web/site2

etc

I had issues with open dir which were solved by an EE expert but thereafter have lost the plot on what the permissions of the folders should be.

I tried having looked at some synology threads

cd ..
DiskStation> chmod -R 777 volume1/web
DiskStation> chmod -R 777 volume1/web/AcousticLaptops

phpmyadmin didnt like that flagged red.

then I tried 750

but now joombla wont install at all

it gives error
Warning: session_start(): open(/var/services/tmp/sess_9iv22prv0klte5pvs092tuif45, O_RDWR) failed: Permission denied (13) in /volume1/web/AcousticLaptops/libraries/joomla/session/session.php on line 658

so I know I have now screwed up the permissions.

so rather than worry about joombla could someone help me with the permissions set up on the synology.

I am unsure of to go via the control panel or folder properties or do in putty with chmod.

I think if I can get this right my issues with web dev would disappear.