What does it mean? We use it as "Must" or "Should". But it means "will". Is it right? And it says "Shall doesn´t use too much anymore" .?

"Shall" and "shan´t" (a contraction for "shall not") are antiquated forms that are not really used in everyday English anymore. People use "will" and "will not." In the old days, "shall" was used with first person and "will" was used with second and third person. It´s a distinction that has died out. About the only place you will hear "shall" used this way is in stage plays and TV shows set in the 19th century. It sounds fancy and old-fashioned, especially to an American ear.

One other usage for "shall" is in expressions such as "Shall we go?" As in the Turkish: "Gidelim mi?" Rather than "Should we go?" -- which would mean "Is it proper that we go?" or "Is it time that we go?" -- one would say "Shall we go?" to get everyone to agree that it´s time to depart. 

If none of this makes sense, just know that you are not wrong to say "will" and "will not" (or "won´t") instead of "shall" and "shall not" (or "shan´t").