Best way to improve credit score?

Hi friends.

So recently I defaulted on a personal loan of 5k due to financial, medical and mental reason.

I have recently paid off this default with the debt company as of last month. But my credit score has stayed low (Equifax says “below average” and one credit score site said it was 157?

What’s the best way to improve this and also is there a way to remove the default or will it stay on my file regardless (equifax report says due to be removed 2027?)

Essentially we want to refinance our home loan when the rate lock ends in May but unsure if we are going to be able to with my default?

Thanks! Much appreciated!