Through the end of act one, a lot has unfolded. The biggest surprise was Linda revealing that Willy was suicidal. Earlier in the play, Biff and Happy believed that his driving problems were caused by Willy being too easily distracted, but Linda told the boys that investigators of one of the accidents saw that he had crashed the car on purpose. To confirm this, The Woman was a witness and saw him driving at a normal pace with plenty of control and he suddenly drove into the side of the bridge, and only the shallowness of the water saved Willy's life. (So, Willy wasn't having an affair either.) Not only, but Willy has been inhaling gas from his heater using a small length of rubber pipe. Linda was too ashamed to show she knew about it to move the tube. 
Everyone knew that Willy was stressed from his age and his money problems, but only Linda knew that he was that bad. His own sons just thought he was going crazy. Once they see how upset and worried Linda is, they decide to stay home instead of moving to the west. So clearly they are more loyal towards Linda than Willy. Even though they used to be in awe of Willy, they still have little faith in him. The act ends with Willy reminiscing about when he was younger and Happy was on a team. This is a very important confirmation, that Willy's depression came because he isn't as young, successful, and respected as he used to be. 

I just finished reading about half of Act I of Death of a Salesman, a play about a middleaged traveling salesman. When the play opens, the scene is the main charecter, Willy, coming home from another sales trip, and he is very late. His wife was worried, and he told her that he had to drife back very slowly because he was becoming so destracted while driving that he veered off the road multiple times. His wife, Linda, was scripted to love Willy even though he has a bad temper. In the next scene, the two sons, Biff and Happy are in bed but still awake. They spend the scene first taljing about Biffs frequent clashes with his father, but laterthey talk about what they want to do for a living. Biff works on a farm making $28 per week. Biff knows that he likes to work outdoors, and Happy agrees on the grounds that everybody in sales is too fake. They fall asleep, and the next scene opens with Willy in the kitchen, and he appears to be mocking his wife, and then he has a flashback. In the flashback, his sons are younger and Biff is getting ready for a football game. Willy and Linda go over the bills and income for that week, and they are $60 short. Willy is distraught and feels he is a bad salesman for many reasons. while his wife is comforting him, he has another flashback involving a similar conversation with a different woman. It seems as though Willy had an affair, but I can't be sure yet.
Biff and Happy in the flashback were almost in awe of their father, but in the present time, Biff doesn't like Willy, so something must've happened to cause the change in attitude. Also, Happy feels conflicted. On one hand, Happy is following in his fathers footsteps taking a job in sales, but he, like Biff, enjoys working outdoors. Also, Willy's affair will most likely cause a conflict later on in the play.