Good day from the Netherlands,
I have a question about load and performance testen with Jmeter.
What is or are good courses? Online is also a good possibility as I am learning more when it is visual. That is also because of my autism.
Another question is if there is a certification for load / performance testen with Jmeter.
JMeter is an open source tool so the chance of having a Certificate is very low.
But there is one company which provides it: JMeter Certification Course | JMeter 4.0 Online Course | Vskills
Although it does look a bit shady (and a few versions behind), I wouldn’t try it because a certificate is just a piece of paper. I don’t think it will have an added value.
If you want to follow a free course: JMeter Beginner Tutorial 1 - How to install Jmeter - YouTube
He explains things very well and it’s easy to follow.
Hope it helps! 
Yes it does help. Going not to take the certification but will follow the free course.