AirBerlin ? Cheap Tickets?

Hello, I really want to go to Europe this summer but my parents think its really expensive we usually go every 2years cause I have family but last year I didn't go. Please can anyone give a cheap and really good airline to go from New York-JFK to Germany and not tickets that are only for one-way but two-way to go and come back ! Thanks you can include any information if you would like to add ! And the countries I go to are Germany , Czech Republic, Swizterland, And maybe Kosova. Tell me who has the cheapest flights for 2-way for the beginning of July.