Babelfish is not a good resource for any approximation of how real people talk (meaning no disrespect to the software or to jespah).
I like you/ I like you too.
Caes bien conmigo (literally you fall well with me).
Caes bien conmigo tambien.
((This is a common idiom. When I first met my wife (who is Mexican) she indicated her interest with this phrase. We were dancing and you can understand how I misunderstood this

)
You could also use "Te Queiro." but this would only be used when you have an intimate relationship and has some strength in a dating dating context.
I miss you/ I miss you too
"Te extraño." or "Te extraño tambien."
What are you doing
"Que haces?" I never hear the gerund used this way in Spanish.
Did you miss me
Me extrañaste?
Buena Suerte.