ALL files should be uploaded in the same folder where your page (the one with the TAF form) is. If snelensimpeleengratiswebsitebouwen.com is your main domain, then the correct folder is your public_html folder, if it is an addon domain, then the correct folder is the default folder of this domain.
It seemes as though none of the three php files are uploaded in the correct folder.
You also have one more problem: you have draged the reset button outside the form area, so it doesn't work.

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