If the tzitzis were pulled and the begged ripped, but the tzitis stayed together, how should I fix them? Is it considered a 4 corner beged if the beged ripped but not totally off? The corner was kind of hanging by one side of the beged. When I stitch the beged do I need to retie all 4 corners, or just the ripped corner?
This depends on the classification of the tear.
If the begged ripped only to some degree, so that it remained a garment with four corners (or with five corners) — meaning somebody who looks at it will consider it a four-cornered garment — the ripped part may be rejoined to the garment, and there is no need to undo any of the tzitzis strings.
However, if it ripped off completely, or close to completely, and the tear itself was curved, so that the garment now possesses only three corners, all the tzitzis strings must be undone, the begged fixed, and the strings ties anew.
Sources: See Mishnah Berurah 15:6-7.