I have nasonex (mometasone) and astelin (nasal spray) but I am not sure wich one will be the best for sinus congestion. Please suggest me which one to take.

They are different. The best first line treatment should include saline nasal irrigation and nasal steroid spray. The steroid spray is long acting and takes affect over the first few weeks of use. The steroid spray helps decrease long term nasal inflammation. Astelin is a topical antihistamine ( like claritin) and can be used in conjunction for symptomatic relief.
Depends. Nasonex (mometasone) is more of a preventative medication uses for allergic conditions. If one controls the allergy then no stuffy nose. For more acute action, the Astelin may be better. It is a topical antihistamine spray of sorts. At your next visit, ask your pcp for advise or your allergist.
There is a differenc. Aster in works well if one has vasomotor rhinitis whereas zn also ex works better in allergic conditions.
Saline wash. If you are not using saline, talk to your doctor about this option since it is the most effective single treatment and the usual first step. It clears the nose from irritants and allergens. Nasonex (mometasone) is a steroid and is more potent (powerful) than astelin; Astelin works quicker than nasonex (mometasone).