API is horibly slow

Hello
I have my Mautic 2.12.2 installation on a Ubuntu virtual machine with php7.0 and Nginx as webserver. My virtual machine runs with 4 cores and 4GB of RAM. I’m heavely using the API to create, update, delete und list contacts and companies in my own application. Everything works fine, beside the performance. Every request I do take like half of a second, which would be fine if I had 10 companies, but I have 8000+ companies. Which would take 4000 seconds to load all of them in my application.
Do you have similar response times when sending a request to any of the Mautic API endpoints?