Cannot understand how to setup a time curve for two keyframes or waypoints?

I need to setup a time curve between frames (or two-points interpolator), e.g. a fast start and a slow end of the animation between two frames or waypoints. Can I do it in Synfig? I’m noobie in synfig, so I need in the detail answer, please.
P.S. I read docs but I understood nothing. Maybe, a reason is my poor English.

Firstly, to be clear, in synfig interpolations are done between two (or three for TCB) waypoints … The keyframes are used to store the state of an animation at a specified time.

I know… it’s still docs… but did you take a look to Interpolation section from Waypoint doc ?

Also, want to say, that synfig have not an easy learn curve… take the time to do the step by step tutorial at the beginning of the doc/wiki (did you saw that the doc/wiki is translated sometime ?) … Also, you can take a look to video tutos (from yt) you have choice of languages.

Thank u for answer!