I hate to say this, all other corrections of "Master's" are wrong.  It has to have the possessive apostrophe if speaking generically.  It is short for "master's degree".  However, if you are speaking of a specific field, then the 's is dropped.  For example, "Master of Computer Science" with the 'm' capitalized.  Same for "Bachelor's" 

Is it correct to say ' "I want to study my master's in Germany"?' ?

Otherwise, how about this? ' "I want to get my master's degree in Germany" , ' I want to get my master degree in Germany.

Colloquially you can also say, "I want to do my Master's in Germany"

Thanks a lot for your help in advance!

Hyunwook

Is it correct to say ' I want to study my master in Germany' ?

Is it correct to say ' I want to study my master in Germany' ?
Otherwise how about this? ' I want to get my master degree in Germany' , ' I want to get my master degree in Germany.

Thanks a lot for your help in advance!

Hyunwook

You could say, "I want to study in Germany to get my masters degree." Or you could say, "I am studying for my masters degree in Germany." :) Hope I helped!

Is it correct to say " I want to study my masters in Germany" ?

Is it correct to say " I want to study my masters in Germany"?
Otherwise how about this? " I want to get my masters degree in Germany" , ' I want to get my master degree in Germany.

Thanks a lot for your help in advance!

Hyunwook

note: You repeated yourself.