I am sorry to tell you, but I'm afraid you'll have to apply the fix yourself ;) As a community we (fellow developers) will try to help you when you have any questions though.
I firstly advise you to check out the available online learning materials (which can be found here: https://gettingstarted.mendixcloud.com/index3.html), in the long run completing these will save you much time.
Regarding the issue at hand: Did you make your pages accessible in your Navigation?
It can also have something to do with your security settings. If you look under project-->settings-->Security, what level of security is applied? If your security is 'off' than this is probably not the issue. If it is on production or demo, than not seeing the pages can be because the specific user does not have access to the page. You can change this in the properties of the specific pages.