I need to improve my credit score quickly

I need to improve my credit score quickly! I am currently sitting at 563 and need it to be higher than 620 to get a home loan. There are 3 collection debts on my account, and I don’t even know what 2 of those are. I was going to negotiate and pay those off as well as all of my credit cards. Will that be enough? I did have one debt that I was behind on 90 days simply by accident…believe it or not which likely ruined me; however, I got that caught up in January when I realized the issue. I’m not sure what I can do to fix all this, but I would like it resolved and my credit score to be higher within 3-6 months. Is that possible?

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use my free credit dispute form and dispute the collections debts you don’t know about
check not your account
paying off your credit cards will help a lot if your balances are more then 80% of your high credit limits
if there is any way to pay off that 90 days behind debt do it
do that before paying off your cards if you can and
 pay each card down less than 80 percent debt