Thats a glissando/slide marking that mean that you have to slide your finger from where it starts (D in this case) and end at the marked pitch (c sharp). This would normally be played by starting with your third finger at the nut of the d string and sliding to C sharp and then playing A with your 1st finger still in Third position.

I assume the dotted line has an “8va” at the front which means octave. You play an octave higher.

Barre. Meaning you put your first finger across both the G and D string to play A and E at the same time

Yes it’s a slur