Nem and Nincs become Sem and Sincs when meaning "Neither ...". For example:
A - "Nem akarok iskolába menni" (I don't want to go to school)
B - "Én sem" (Neither do I)
A - "Sajnos nincs pénzem" (Unfortunately I don't have any money)
B - "Nekem sincs" (Neither do I)
Note that you can also say "Se" instead of "Sem" ("Én se", for example)
Sincs is used in place of most instances of ∗is nincs or ∗sem van, whichever way you think about it. Ő nincs itt means He is not here, Ő sincs itt means He [as well as other people] is not here.
Ownership in Hungarian is expressed a little differently than with a verb "have". Instead, they say something like "For me, there is [object]" - "Nekem van [object]." So in turn, "Nekem sincs [object]" means "I do not have [object] either." This where the hint comes from.
could someone explain the difference between nem and nincs ? sem and sincs?
Nem simply means "not". Nincs, on the other hand, is a verb. It's the lovechild of nem and van, so whenever you would write "nem van", you use nincs instead. It means "there is no", or if related to locations or times, "is not". It's the negation of van, of existence. It also has a plural form, nincsenek - "there are no" or "are not".
Sem and sincs have the same relation, but sem is a combination of "is nem", meaning "not either". As a result, sincs means "there is no... either" or "is not... either".