Time depends on experience, but expect to spend 1-2 hours or more per 10 min when you are on an intermediate level. However, there are so many things that affect the time it takes. Hand- and blowjobs takes much much longer if you do it properly while simple parts might even be automated with motion tracking tools.
Links if you want to learn scripting:
https://discuss.eroscripts.com/t/how-to-script-in-openfunscripter-video-tutorial/16637
https://discuss.eroscripts.com/t/how-to-get-started-with-scripting/2234