Assess Server Requirements

My server is a VPS hosted by Interserver.com. It runs on Apache 2.4.39 with Centos7 Pro. There is 4Gb RAM, 125Gb Hard Disk space and 4 CPUs. There are 3 sites on the server – each has a separate CentosWP control panel. There are also several SMTP email accounts on the server, all related to the 3 sites, which send out around 100 emails per day via a WP plugin called Arigato Pro. My desktop email client Thunderbird accesses the server to receive emails sent to me. Several freelancers have commented that the server is inadequate for the following reasons: 1. It requires a lot of pings or bouncing around before it can be reached; 2. Centos7 Pro will not be supported long term; 3. The hardware is old; 4. The Linux version is ancient – I think it's v 7. Experientially, I find that the server is often offline, and sends overload messages almost every day. The attached file shows some of the notifications I receive. The 3 sites receive only around 300 visitors per day in total. Something is very inadequate. So I wish to update my OS to the latest Ubuntu, and maybe find a different hosting company. However when I investigate the alternatives to [login to view URL], the specifications are confusing. They are too numerous and complex. I'm not a technical guy. This job requires someone to assess my server needs and recommend alternatives. Specifically I want to know: 1. How much would it cost per month to host the 3 sites on Oracle? 2. How much would it cost per month to host the 3 sites on Amazon? 3. If I migrate to Oracle or Amazon, I will need to route emails via Amazon Simple Email Service. How much will this cost? 4. How much would it cost per month to host the 3 sites on the best other server that you know of? Bid your price for the job, not your hourly rate. NO emails or phone calls: Freelancer applications only.