A (沒關係) 没关系 mei2 guan1xi 
never mind/ it doesn't matter 
das macht nichts B (沒什麼) 没什么 mei2 shen2me
it doesn't matter
nichts, keine Ursache B (沒事兒) 没事儿 mei2 shi4r
it doesn't matter
nichts vorhaben,nicht von Bedeutung
Definitions from Unihan Copyright © 1991-2015 Unicode® Inc. All rights reserved.
沒 没 not, have not, none / drown, sink
事 事 affair, matter, business / to serve / accident, incident
兒 儿 son, child / KangXi radical 10
from CC-CEDICT under a Creative Commons Attribution-Share Alike 3.0 License
B (沒事兒) 没事儿 mei2 shi4r it doesn't matter nichts vorhaben,nicht von Bedeutung Definitions from Unihan Copyright © 1991-2015 Unicode® Inc. All rights reserved.
沒 没 not, have not, none / drown, sink 事 事 affair, matter, business / to serve / accident, incident 兒 儿 son, child / KangXi radical 10 from CC-CEDICT under a Creative Commons Attribution-Share Alike 3.0 License