Automatic transmission

My transmission is not shifting correctly. Reverse works fine and 4th gear also works fine. 1st, 2nd, & 3rd are not working at all. I had a slight accident, I drove into a roundabout that was recently added to a very dark area ( at night). Anyway put a hold in my oil pan, did a little exhaust damage and passenger CV joint damage. All have been repaired. When I went to drive it I realized that I am starting out in 4th gear. Tried to down shift to 3rd and nothing same with 2nd and 1st. Tried taking off in 1st gear and manually shift up the gears nothing just 4th gear. Checked fluid level and color. All good. Doesn't grind or make noise of any kind and actually drives great once I'm going fast enough for 4th gear. I have put so much $$ into repairing the damage from that roundabout I didn't know was there. I am hoping you will have an answer for this problem. What is wrong with it?