It appears to be a copy of a Honda CG125... if that's the case, 10w-40 is fine for it, and there isn't an oil filter in particular. There is an oil slinger that can be cleaned under the right side cover, which must be removed. Inside you'll find a cover that appears to have Phillips head screws on it. They aren't Phillips head, they're a head called JIS.
They look the same, but Phillps heads are designed to cam out with excessive torque, JIS are not, so what will happen is that you'll not be able to remove the screws with a standard Phillips screwdriver, you'll ruin the screws instead and not be able to remove the cover.
To save you the trouble, get a proper JIS #2 screwdriver:
https://www.amazon.com/Vessel-Megado...dp/B000TG8OTY/