measure widened when I uploaded a piece to musescore

It shouldn't but I prefer to use the start and end note selection. In the attachment (*Ter) I have resized via Format/Page Settings->Scaling

Dragging anything more than just a slight amount is likely to cause at least some issues. It's important elements be attached properly. You can't add a marking to one note then drag it to appear above/below another note and expect it to work properly.

In the case of your slurs, the very first one is indicative of this, but they pretty much all have the same flaw. It's actually attached only to the first two notes, then stretched to look like it covers a whole measure and then some. So if the width of the measure ever changes, that slur is going to be very dadly wrong - either too long or too short, depending on whether the measure got narrower or wider.

In the future, when adding slurs, select the full range first, then click the palette icon or shortcut "S". but to fix existing incorrect scores, select one, press "R" to reset it, then use Shift+Right to extend it properly a note at a time.

The reason the measure widths differ on musescore.com is, I think, that you seem to be using a font for lyrics that musescore.com simply doesn't have. So it is substituting something else, and the widths differ. BTW, you're also doing that incorrectly I'm afraid - you're using the text toolbar to change each lyric one by one rather than simply changing the lyric text style. Your way is much much much more work. doubly so to fix the problem now. To fix it, right-click one lyric, Select / All Similar Elements, then click the "Remove Custom Formatting" button in the Inspector. You should also hit the reset buttons next to the font field. If you still wish to use a font other than the default, change it there in the Inspector then hit the set as style button ("S") icon. But do be aware that the score will look different on musescore.com as well as as the systems of anyone who downloads it.