Can you turn off male moans and just have female moans in sex scenes?
In most Renpy games all Music is controlled by Music Volume, all background sounds/ambience is usually controlled by Sound Volume, and sex sounds/voice acting/moans is controlled wholly by Voice Volume. It's all coded into that one specific volume slider, so you cannot turn off male/female moans separately, only mute all voice sounds.
If you felt like doing more work, you could delete male audio files and rename any other .mp3 file to that deleted file name, from the audio folder or the audio.rpa archive. If it's an archive, you'll need to unpack the .rpa using UnRen (use the search function on the main F95 site page). Messing with game files like this is at your own risk, it's not guaranteed to work, and it may likely cause errors, so you'll have to troubleshoot and fix it yourself. Depends on how badly it's bothering you, and much willingness you have.
PS- I haven't played this game recently, but this method should work in general for any Renpy game.
how do I change the language in the game? There was a choice on the right side of the main menu, but now it's gone....
If you right-click or press Escape, in the options listed on the left, select "Preferences", from there you can change any settings including Language. But, the language option only shows up if the game has scripts in multiple languages. In the OP you can see, other Languages are only updated to v0.9, so v1.0 current update doesn't have anything other than English.
Since, this says BETA, I'm guessing there will be another finalised "Final" version, which will have all languages. So you just have to wait a bit.