Go to Al Fakha (very small shop in shj) guy name is Ameen, its behind BM road on side of Alico. Few years back he fixed my polo with same problem, i think it need cleaning, and changing of small filter doiwn the radiator and full freon leak test and top up. Guy is so honest that he charged me just 200 dhs 2-3 years back.
050 7373910, give my refernce of white polo 2001 model and he might remember as he dont know me by name, and till date im going to him and coming back happy. Hope he able to help you.