Actually, WP Travel Pro plugin is the bundle of all the modules and features. So, when we activate WP Travel Pro plugin all the features and modules will be activated which is the reason for the slow speed.
So, please disable the modules which are not required for you by going to Admin Panel > WP Travel > Settings > Addons Setting as shown in screenshot given below.
Also, please disable unused payment gateways by going to Admin Panel > WP Travel > Settings > Payment as shown in screenshot below.
If you have any queries, please submit it to our contact page.