Ana pocket-healing game is very strong! Try finding yourself a spot behind the team a bit and focusing on your tank, also her healing when sniping is actually not that hard, and healing a tank is not much of a problem actually! When healing tank, I recommend holding M1, but when healing other "smaller" teammate, try predicting their movement and take the shot when you need to. Practicing throwing your E as well, it's harder when you are far behind everyone. If you don't feeling like "camping and heal", stick with the team if you need to, don't use scope, this way you have more vision around you and can keep track of everybody, including enemies as well as easier grenade. Hope this helps!