Problem with Gate installation on Linux

[maikeros]

I installed Gate with: sudo snap install gate
After that I am able to open the program, but if I try to execute a macro, I always get the following error:
I/O error : Permission denied
I/O error : Permission denied
I/O warning : failed to load external entity "./Materials.xml"
I/O warning: Discard the previous warning if your simulation doesn't transport OPTICAL PHOTONS.
Otherwise, please copy the ./Materials.xml file from the gate-source directory in the directory where you run your main macro.
I/O warning : failed to load external entity "./Materials.xml"
I/O warning: Discard the previous warning if your simulation doesn't transport OPTICAL PHOTONS.
Otherwise, please copy the ./Materials.xml file from the gate-source directory in the directory where you run your main macro.

I tried to open the program as sudo, but than he doesn't even find my macro anymore. I had this problem on two different computers now. Any ideas, what could fix the problem? I am totally new to this kind of simulating and programing, so maybe it's a stupid question.
Thank you!

[maikeros]

Additional note. When starting Gate, it says:
update.go:85: cannot change mount namespace according to change mount (/snap/gtk-common-themes/1535/share/gtk2/Materia-compact /snap/gate/41/data-dir/themes/Materia-compact none bind,ro 0 0): cannot write to "/snap/gtk-common-themes/1535/share/gtk2/Materia-compact" because it would affect the host in "/snap"
update.go:85: cannot change mount namespace according to change mount (/snap/gtk-common-themes/1535/share/gtk2/Materia-dark-compact /snap/gate/41/data-dir/themes/Materia-dark-compact none bind,ro 0 0): cannot write to "/snap/gtk-common-themes/1535/share/gtk2/Materia-dark-compact" because it would affect the host in "/snap"
update.go:85: cannot change mount namespace according to change mount (/snap/gtk-common-themes/1535/share/gtk2/Yaru-MATE-dark /snap/gate/41/data-dir/themes/Yaru-MATE-dark none bind,ro 0 0): cannot use "/snap/gtk-common-themes/1535/share/gtk2/Yaru-MATE-dark" as bind-mount source: not a directory
update.go:85: cannot change mount namespace according to change mount (/snap/gtk-common-themes/1535/share/gtk2/Yaru-MATE-light /snap/gate/41/data-dir/themes/Yaru-MATE-light none bind,ro 0 0): cannot use "/snap/gtk-common-themes/1535/share/gtk2/Yaru-MATE-light" as bind-mount source: not a directory