Can I firstly get confirmation that the hole marked in the photo is the filler hole?
Yes, it takes circa 2 litres of oil and with the car on level ground it should be filled to the point where it’s just about to overflow.
As to your oil, there are threads in the forum on what is suitable but remember, oil is cheap, gearboxes aren’t, just like engines, so it’s not worth skimping on fluids for them……
David Faulkner