Round Up is not permanent. You can reseed two weeks after an application. For killing weeds I prefer some of the off brands and find they actually work better. Round Up's main ingredient is glyphosate but it also contains a chemical for quick results. You spray in the morning and by that evening you already see some wilting. Problem with that is in order to kill the weed the glyphosate needs to be drawn down into the roots by the leaves of the plant. Once the plant is wilted and brown it's not transferring anything to the roots. I use either the Groundworks brand 41% glyphosate from Tractor Supply or the Eliminator brand from Walmart. Neither of these contain the "happy chemical" that kills almost immediately like Round Up. You can expect either of these to take about a week before you see results but by then they have already drawn the glyphosate down to the roots and you get a better kill. I do mix in dish detergent with both of these to help them stick to the plant but overall it's much cheaper with better long term results. That being said, you can use a small paint brush and paint the glyphosate on the leaves of the weeds. I've done this in the past with great results with little or no damage to the surrounding good grass. Only down side is if you have a lot of weeds it can be extremely time consuming.

The wide blade one is either an old style fescue, like Kentucky 31, or a weed grass. Hard to tell from the one pic. Its a clumping type grass. When I see one in my yard, I just grub it out and either re-seed or stick in a bit of sod to replace it. That grass seems to want to grow along hot sidewalks more than my improved grasses, so, sometimes there I will just dig out a length of it and lay sod in its place along the concrete.

If you have nothing growing in that area besides the quackgrass and weeds, you can kill it off by smothering it. Lay down section-thick layers of newspaper or cardboard and cover with mulch. Watch for any creeping runners coming up at the edges. Within a year it should be dead. It is a very hardy weed and would probably need several applications of Roundup to kill it, so that is up to you environmental-wise. If, however, you have any desirable plants growing in that area, the quack grass entwines its roots with other perennials and is impossible to completely eradicate by pulling. You are lucky if you are working with a so-called blank slate and can do the smothering solution. I have this weed in my garden and I swear one of its genetic adaptations is to quickly find perennials with a good root system to entwine with, because it knows it will therefore survive because the gardener will never be able to separate the two. I have even dug up plants and tried to separate the quack grass roots from the perennial but have never gotten it all. I do find that it pulls easiest in the spring and fall, and I have less of it year after year as I spend a bit of time pulling runners. In summer it really entrenches itself and nearly always breaks off when pulled, only to regenerate from whatever's left in the ground.

If only a small area of the lawn is affected, you could try to dig out the quackgrass; but all the rhizomes must be removed because rhizomes as small as 1/2 in. can produce new growth if left in the soil. Frequent, close mowing can be an effective way to control quackgrass on lawns of bluegrass or fescue.