On the website you can see, the mobile app is missing some functionnalities
Actually, W is not part of the official Esperanto alphabet along with Q, X and Y. However if it is not obvious we use x when there are difficulties in typing out the diacritics.
Do you want the long answer or the short one? (Seriously, I'd be happy to provide either.) Short answer is that it depends a lot on context, but it's best to think of "varma" as "hot." That would make "varmega" to be "broiling" or "scalding" or some other word along those lines.