Fix it in 3 months???!!!
Sorry
but that isn't really possible.
What you could do is improve it enough for a decent crop and start the process of fixing it .... which will probably take at least 3-5 years or more, depending on your skill as a gardener.
step 1 Get the soil tested, usually cheaply done through the local extension office or local state run university.
step 2 Furrow it for drainage. The furrows don't have to be deep. 6 inches usually is enough. The furrows should be fairly wide though. Use the soil from the furrows to raise the beds slightly. A good rule of thumb is 3-4 feet wide "beds" with at least 2 feet of furrow making a path between beds.
Step 3 Cover EVERYTHING, furrows and beds with either 6 layers of newspaper covered with 6 inches of hay/grass clippings, or cardboard covered with 6 inches of hay/grass clippings.
Step 4 Wait 3 months and plant in the beds right through the mulch, and ONLY walk in the furrows. At this time make amendments suggested by your soil test.
This is an emergency gotta be done in 3 months without any budget fix it for now plan, not to be confused with the many possible long term strategies.