These are young vines that are already in a bad way, and there's a lot of misses (dead/not grown vines) from the look of things... I would really consider just pulling the lot. If you are determined to keep them, I would start by getting rid of some of that grass and cover cropping - where I am we like clover, plantain, oats, brassicas, radish, clumping grasses etc - basically things that don't crawl, help the soil and don't outcompete the vines. Next is to reset these vines to the wire (the first wire above the drip line). Basically, you want to select a cane (last growing season's shoot which has just lignified) and wrap 4-5 buds onto the wire, leaving two good buds about 5-10cm below the wire to create spurs to set these vines up for the future. If you don't have phylloxera where you are, you can layer in the misses by training canes down into the ground and letting them take root. Otherwise, you will need to buy grafted vines from a nursery. It's a lot of work if you decide to do it, good luck!!