Thanks for playing! Maybe you should've played the tutorial then :D because it explains the most important features thus how to progress. You should have scaled yourself down to move to a crack in the wall at the upper room in order to open a chest with the blueish key, of with you would get the last key needed to progress :) you can also watch the youtube playthrough in case you wanna see what would've come next. Anyhow, glad that you enjoyed it nonetheless!