Wordpress + Database + PHP Optimize & SEO

Hi. I'm looking for a expert who can help me

1. Optimize my MariaDB on my Ubuntu VPS.
2. Fix my 3 Wordpress sites. Because PageSpeed Insights show me so bad results.
3. Optimize PHP. I'm using DirectAdmin
4. Fix my JSON URL sites. Because query so slow.

Ideal Skills and Experience:
- Extensive experience with MariaDB and MySQL
- Proven track record in database optimization
- Familiarity with Ubuntu VPS and DirectAdmin
- Knowledge in PHP, JSON and WordPress.

I have three wordpress websites:

1. https://www.viacast.eu
2. https://www.equidash.eu
3. https://www.holaevents.es

All these pages performance test must be max results. All these pages needs SEO and this must be max results.

I have some JSON url which must be works quickly, but now response makes so much time.

1. https://equipe.viacast.eu/vmix/rider_dressage_result.php?ID=QR123

2. https://equipe.viacast.eu/vmix/top5_dressage.php?ID=QR123

3. https://equipe.viacast.eu/vmix/startlist_dressage.php?ID=QR123

4. https://equipe.viacast.eu/vmix/rider_dressage.php?ID=QR123

5. https://equipe.viacast.eu/vmix/leader_dressage.php?ID=QR123


NB! IF YOU LACK REAL EXPERIENCE OR DOUBT YOURSELF, DO NOT OFFER YOURSELF, BECAUSE THE PAGES AND THE SERVER ARE IN DAILY WORK AND YOUR IGNORANCE OR MISTAKE COULD CAUSE SEVERE CONSEQUENCES