You can RUIN your credit quickly. Repairing it takes time…
Repairing bad credit is like a diet. It requires time and diligence. You don’t repair bad credit. You re-establish good credit.
Your credit is actually two different things. You have a credit score, and you have a credit history. They are not the same.
If you have multiple derogatory items on your credit report – with time their impact on your credit score will diminish. Resolving them won’t raise your score. Never the less – you need to resolve them because no one will approve your applications for credit with unresolved derogatory items on your file, regardless of your score.
Establishing good credit requires time and diligence. You need at least 24 months of consistent timely payments. If you can’t get a regular credit card you’ll need to apply for a secured credit card.
The only “quick” thing that you can do is lower your balance to limit ration (credit utilization) below 35%. This should result in a 50 point raise in your Fico score, but other than that, you’re looking at a long period of time and hard work.