Wordpress delay when try use contact form

Hi all!! I 'm very frustrated about my issues with DO Droplet, please a good man that help me! I am owner of droplet where i run few wordpress sites, all work great, but when i try do some actions on a website that need several seconds to do, actions like:

• add comments
• add new user from back-end
• change user password from backend
• send email from contact form ecc ecc

i Have not set a mail server, only use sendmail, where i add all host of my domains

Please can a good man help me about that? Thank You Stew