Dear Fai,
The mantle of your adult gull is not dark enough for Heuglin's Gull, the black on the wing tips is not extensive enough and the underside of the primaries and secondaries does not appear dark enough. I think its a Vega Gull for the following reasons:-
1. Mantle colour is mid-grey.
2. White trailing edge to upperwing is very broad [shares this with Slaty-backed].
3. Extent of black on primary tips is right for Vega.
4. Has two wing mirrors with the larger on the outer primary [p10] extending to wing tip [some Yellow-legged/Mongolian have this too but the strong neck streaking rules out this taxon].
5. Grey tongues on upperside of mid primaries have white tips, which again is typical of Vega.
6. No sign of wing moult. This fits Vega where most have now completed wing moult whereas most Heuglin's would still be completing new outer primaries.
Cant make out leg colour but would expect it to be pink.
Mike Chalmers
