I have this piece of music where there is a simple melody (about 4 measures) that is slurred and harmonizes with an open G. The melody on top goes up to high E in the staff.

Here are my questions:

1)How do I shift from third position to fourth position while slurring?

2)How do I sustain a pitch in one bow for that long?

Any advice would be unimaginably appreciated!(from experience is preffered)

try practicing just shifting from one double stop to the next slowly and then go faster gradually until you barely even here the shift and you are very comfortable with it.

for the right hand: try just playing on an open string, moving the bow as slowly as possible but still making sound (even if its not very pretty). then apply this to the double stops and try to make it sound better by getting more comfy with the long bows.