Please fill out the fields below so we can help you better. Note: you must provide your domain name to get help. Domain names for issued certificates are all made public in Certificate Transparency logs (e.g. https://crt.sh/?q=example.com), so withholding your domain name here does not increase secrecy, but only makes it harder for us to provide help.
That's bad. It should be possible to download or backup the private and the public key, then you can reuse both files.
Letsencrypt certificates are free, but not unlimited.
Perhaps. Is it possible that you create one certificate with a lot of domain names and use that?
I don't use VestaCP, so I don't know if there is such an option.
The rate limit - 5 identical certificates per week. Identical -> the same set of domain names. So if you use another set of domain names, that may work.