Problems due to new landingpage: URL Change

The cms of the my website  is created by an agency.

I asked them to create a landingspage. This caused a change in the URL structure. To clarify, first an url such as www.x.be/nl/contact was indexed (and visible in Google). This is how it should be. Now www.x.be/nl/Main/contact is indexed. To clarify, due to the change, “main” was added in all the URLs  and They added a canon tag on the url with” Main”.  As a result, The original urls are not indexed anymore.  I was not happy with the URL structure and suggested 301 redirections (from the URLS with “main”) to the original urls. That was not possible for them . Now I have also issues with Google Analytics as I see different results for both URLS. I see for instance only results until march for Www.x.be /nl/contact and after they changed the urls I see results for www.x.be/nl/main/contact. What did they do wrong with the landingspage? How can I fix this?