Should you say Gesundheit?

This depends on the context. You might say "Does your mother want a drink?" or "Do your homework" but to switch them would be incorrect.

Don't say anything that will get u imbarrased, and don't say too much information about yourself to the person unless they're your friend , and dont share too little. Then they'll think youre...

Tell her you love her

rejection is very hard, but a natural human feeling.. don't ask her why she said no.. just breathe, take it all in, and try to forget about the situation for a while... if you really liked this...

i'd say you and he... Keep it simple: Say "we" or "us"