(1)I got 12 x330w solar panels but the average power generated from the sun is 8.2kwh per day is this average  or should it be higher

(2) I got a 5.12kwh Sotho Lithium  but it is always  over 90% full how can change my settings in the inverter to use more battery power  during the day before it get charged for the night?

Not sure which inverter you have, but try changing to SBU mode (Solar, then Battery, then Utility) and then you can use the 'back to grid' and 'back to battery' settings to control how much battery you use.

Thank you will try that