Hello, thank you for your answer. I found out what was the problem with the icons not showing properly. I deleted all and started from scratch again. It was the ELEMENTOR Plugin that did something for them not to work. So ELementor is probably not suitable for Writer’s Blog Theme. I deinstalled it and do now use the SiteOrigin Editor, and that works well.
I also just took WPForms for making the Contact Sheet, and that also works well.
Now I do no longer get the message to install Instagram Plugin. it was also installed before, but always I would get the error message that I have to install it. Hopefully my website will work now.