(I) have been studying for one month.
Ikkagetsu-kan benkyo shite imasu.
Yes, but only a little.
Hai, demo sukoshi dake desu.
How long have you been studying for?
Doregurai benkyo shite imasu ka?
(Your) Japanese is good.
Nihongo ga ojozu desu ne!
A little more slowly please.
Mo sukoshi yukkuri onegaishimasu
How long have (you) been studying Japanese for?
Doregurai Nihongo o benkyo shite imasu ka?