Parntership buy out

There needs to be a bit more clarity.

There still is a partnership?

The partner that stepped away wasn't bought out by any other partner or the partnership itself? What happened to their share of the partnership, then?

One partner cannot sell the partnership assets if the partnership owns the assets. Or, the partnership first distributed/sold the assets to this one partner, who then sold them as an individual?

How does the partner "that sold" also still own "very little" interest? What did this person sell? What did they retain? Who did they sell to? What did they sell? Which partner is this: the one that stepped away, the one that sold something not belonging to them? Object and subject are a bit confused, here.

You stated the partnership name was sold, but does that entity still exist? The Partnership continued operating under a new name, or formed a new partnership or is dissolved or dissolving or no longer in business or?

"the new partner that now owns 99%."

Then this makes no sense: "How do I add the new partner and "sell" him the assets"

It's one or the other:

The old partner pulled the assets from the partnership, and owning them personally, sold them to an individual.

Or;

The partnership still owns assets, and the new partner bought into the partnership, and the value of the assets are part of the justification for the buy in.

Or, I suppose:

The old partner pulled the assets out of the partnership, sold them as an individual, to another individual, who owns them personally and wants to contribute them to the existing old partnership? Sheesh.

Nice people or not, none of this is making sense. Ownership matters.

"Note to add that the sell is on a 0 interest monthly payment plan"

There is no such thing as 0 interest in business.