Hi,
i dont think there is a any problem with WP, i think is need to look up on server tips.
Need to take a look at website URL, and also can you tell me what kind of server you use:
1. Shared Host with CPanel like HostGator, Godaddy... etc
2. VPS - Virtual Private Server like DigitalOcean, Linode... etc
3. Or Dedicate Server
btw, I can provide you any service for Your website needs from scratch till the end.
From Server installing, to WP setup from scratch, setup WP Themes, Plugins, customize it, helping you with advice from my more than 15 yrs experience (Drupal, WordPress, Ubuntu, CentOS...)
I can be helpful in long term in solving any "ad hoc" problem, advice or work.
Please feel free to contact me for any info you need.
Best Regards
Dragan Petrovic