Toilet Flapper Sticking

Had to replace ball valve on Thetford AquamagicIV. While I had it out replaced flapper gasket. Could not seem to get it to work right as I am not sure which way flapper should face. Also old spring was not holding flapper tight. New spring was smaller and heavier gauge and would not stay in place. Ended up with combo of older spring and newer spring trimmed down and slipped inside old spring. Now the flapper sticks open and must be encouraged to close. Where did I go wrong?