Buy Together Module Add To Cart Very Slow

Hi, I'm using the buy together module.
Press the add them to the basket button,
It's waiting for 20 seconds.
5 different sites in this way.

I couldn't find the reason why it takes a long time to get into the basket.

time to add single product to the basket is 2 seconds.

this is 20 seconds with the purchase module together.
is there a solution?

4.8.1 sp1