"Flags" invaded half of my music and I can't undo it...

I was trying to select multiple parts of the song to copy and paste it for a repeat in the music and when I was trying to figure out how to select part of a measure instead of the whole measure I believe it was something like ctrl and shift at the same time and then I tried dragging something and everything just went crazy on my screen. I could only undo a portion of everything that happened and my music still looks really weird haha. I can't seem to delete the flags either and I don't really know how to adjust the spacing. I'm very new to this software and honestly clueless. Any help would be appreciated. Thanks!