If you have negative information on your credit report, it will remain there for 7-10 years. This helps lenders and others get a better picture of your credit history. However, while you may not be able to change information from the past, you can demonstrate good credit management moving forward by paying your bills on time and as agreed. As you build a positive credit history, over time, your credit scores will likely improve.
If you find information that is incorrect, you can file a dispute. Remember too, that items on your credit report that you don't recognize could also be potential signs of fraudulent activity — someone working to secure credit in your name for their own use. Make sure you're clear on items that could potentially be fraudulent, versus those that may simply be inaccurate.