To complete the Sweet’s Girl mission in GTA San Andreas: Definitive Edition, you need to put the crouching and shooting skills you practiced at Emmet’s place into use in a real shoot-out. The mission begins when you enter Sweet’s house and discover that no one is home. After looking around for a little while, you’ll go outside and receive a call from Sweet. He tells you that he is pinned down in the Seville ‘hood and needs a ride home.
Get in a car (there’s a Picador parked outside the house next to CJ’s) and, if you don’t already have a gun, drive to the red dot on the mini-map to buy a gun from Emmet. Otherwise, follow the yellow line to the Seville ‘hood. When you get there, resist the temptation to plow through the Seville boys on the sidewalk in front of Sweet’s Girl’s apartment. They’ll shoot up your car, and that’s likely to leave you exposed or, worse still, dead.
Instead, park on the opposite side of the street and crouch behind one of the low walls. From here, you should be able to take out all of the Seville boys without taking much damage yourself. Most of them are close enough to auto-target, but you’ll probably need to use manual aim to get the one on the steps.
Once all the Seville boys are dead, Sweet will call and tell you to get a car. Don’t use the one that the Seville boys have clustered around, as it will have been damaged in the shoot-out. Hijack a car in good condition and drive back to Grove Street. Seville boys in cars will chase you, but just let Sweet deal with them while you keep your eyes on the road. They won’t chase you all the way back to Grove Street anyway.