Totem cuts the image when in complete screen

This sounds like a bug. I suggest reporting it as one, if you have not already done so. See https://help.ubuntu.com/community/ReportingBugs. You can search at https://bugs.launchpad.net/ubuntu/+source/totem to see if it's already been reported.

Have you tried playing the video in a different player, such as VLC?

I've tried VLC as well, but it seems that it can not play something in fullscreen if the original screen, the one in the laptop, is smaller than the second one(which is the one that i'm trying to play the fullscreen on). Changing the resolution kinda solves it, but you get a crappy video in 4:3 instead of in 16:9.

I'm not sure if this will help you, but in VLC, you can set a video's aspect ratio manually by going to Video > Aspect Ratio.

If you still want help with this issue, you should reopen this question (i.e. set its status back from Answered to Open). When you post, you can reopen it by clicking the button for asking for further assistance, instead of the one that says "Just Add a Comment". If you are no longer soliciting help with this issue, then you should mark it as Solved. If you report your issue as a bug, you can make a link to the bug report appear in this question by using the link (in this question) that says "Link existing bug". Doing that will not, in and of itself, change the status of this question (so, for example, you can link to the bug report but keep the question open if you still want people to help you in the question).

Thanks i've reported the bug and i will reopen this issue.

Your bug report is lacking some important information, detailed at https://help.ubuntu.com/community/ReportingBugs. After reading that, you should edit your bug report to provide the relevant package version(s) and attach the the relevant files with apport-collect, or mark the original report as Invalid (commenting on it to explain why) and submit a new report. If you submit a new report the best way to do it is to go to Help > Report a Problem... in Totem, or (also with Totem running) press Alt+F2 and run the command "ubuntu-bug `pidof totem`" (without the enclosing double-quotes). Note that the text "pidof totem" is enclosed in backquotes (on a US/English keyboard, same key as ~, but don't press Shift), not apostrophes. You can copy and paste that command.

But please don't take any of this as an indication not to read https://help.ubuntu.com/community/ReportingBugs first.