I have a unstable  Hashrate, i’m mining Ethereum by Genoil
my hardwares:
Graphic card: Asus Rx 480 4gb OC
Motherboard: Asus Z270-p
Ram : Furyx 4Gb
Hard:320Gb sata III (unknown brand)
CPU: intel Pentium G4400
Power: Green 485W (Used but tested)

i’m on Overclock mode and here is my hashrate: (20MH/s)
http://imgur.com/a/UBBfh

and my profile on Ethermine.org:
http://imgur.com/a/CaJN1

and finally my command who i’m using in Genoil:
ethminer.exe --farm-recheck 200 -G -S eu1.ethermine.org:4444 -FS eu2.ethermine.org:14444 -O <my wallet>

Questions:
1.
i just started yesterday, Do you know why i have Unstable hashrate?
(“Current hashrate” on Ethermine.org)

2.
why my hashrate can’t raise in Genoil more then 20MH/s?

why i have about 5% stale shares on Ethermine.org?

Regards