Zdravo Alaa! Your Serbian is very good for someone who has just started learning! I've corrected the mistakes you made, but they weren't big. Everyone in Serbia would have understood you. Have a nice day :)

Ja sam Ala. Živim u Srbiji, na Avali (personal nouns start with a capital letter and this is the name of a mountain) gde učim srpski jezik. (instead of making a new sentence, you can connect the two with "gde" which means "where". You are learning Serbian in Serbia.) Da li biste mogli da mi pomognete? (This is a polite way of asking if people could help you) Na slici je prelepa reka Dunav. ("Ovo" would be used if you were physically with us, showing the river with your finger. Since you uploaded a picture, it is correct to say so by saying "na slici", which means "in the picture") Srbija ima mnogo lepih mesta. (Serbia has a lot of beautiful places.) Welcome to Serbia, Alaa! Enjoy your stay! You're doing a great job with your Serbian!

Bravo Ala. Samo tako nastavi.