That’s not how it works.
No offense, but I’m not your personal technical support and not obliged to do anything specifically for you or be anything specific for you as long as I’m acting within forum rules. When people misunderstand something, be polite and explain stuff to them. Then you’ll get help.
Now getting back to your question:
Select a bone, go to graph editor view, set extrapolation mode to Cyclic and check if curves look smooth. Extrapolation mode can be changed via channel menu.
Also, by default blender uses bezier interpolation for animation curves, so you could move bezier handles around and get desured rate if change (even non-linear one).
In some cases it is simpler to set interpolation mode to “linear”, though.
Interpolation mode can be changed via Key menu. Available modes are linear, bezeir and constant.
For smooth looping animations you’ll need to set “Extrapolation” mode.
To make some animation speedup or slowdown between keys, change “interpolation” mode.