ErrorThis filetype is not allowed, Save failed wit

Hi, Congratulations, I save a lot of time with your tool. 

I have some problems with the form, I try to use 3 types of files, png, jpeg, gif but when I try to save the information I get the following: 
ErrorThis filetype is not allowed 
This filetype is not allowed 
Save failed with the Following error: 
Then I would like to use a field that verify emails and a Captcha to prevent the robots to insert data, but I can't find any on the list of fields
any tips would be nice
Thanks in advance

U need to u mime type instead of fill in like "png,jpg,gif". For a complete mime type, you can see here www.freeformatter.com/mime-types-list.html