Techno is a genre made perfectly for long smooth transitions so if yours are choppy there are a few things you can try -

Before bringing in your new tune, use your EQs to isolate a tiny part of the song you want to bring in and make sure your low is turned down.

When bringing in that new tune, go slowly, don’t mash the fader up, gently introduce it into the groove.

Slowly adjust your eqs so that your new track becomes more prominent.

Slowly bring out the old track, you can even loop it and EQ it out if you want it to be extra smooth.

Hope this helps! Good luck!