E-shop Woocommerce problem

there is a project with woocommerce i have setted a website with ~77.000 the problem is that we need this to be refresh everyday 3 times a day.. for now it is setted at once. the problem is that everytime it runs the the server load going to the MAXIMUM. we need to set it through cron job as it is already and find the problem with the high load.. also we need to set it to be done 3 times a day and find a way for this to finalize the working at maximum of 2 hours each time.

the project i have is e-shopaki.gr and i am seting in back the /b2b in which i need to work as supplier i have
wp all import
wp all export
for these crons

also i have setted the xmls