Canvas sewing is a definite skill, but it can be learned.
(I'm lucky, I came from the sailing world, and spent many hours repairing old canvas sails)
I'd recommend a sailmaker/leatherworker's awl, like the Speedy Stiitcher,.
As already noted, use a UV resistant thread, and wax it. It may say "waxed" on the label, but I would recommend drawing the thread over a block of beeswax. It helps to seal and waterproof your stitches, and lets the thread slide more easily as you pull it through the canvas. And it smells nice..
For a repair of that size, you will need to sew in a backing piece of canvas or a heavy fabric tape, a couple of inches wide.
It can be a pain, but it's curiously satisfying.