Obtaining comparative offers sounds like "I actually want something else." Selling is a tough business, keep doing viewings, either someone wants it or not. I wouldn't renegotiate with so many inquiries, if anything, the price might even increase through 2 or more interested buyers. Real estate agents master this perfectly.
The number of interested parties actually indicates that it is too cheap.
Just do open house viewings. You will get more people through and the competition can already look each other in the eyes.
.....I don't think it's too cheap. There is almost nothing on the market here and most of it is overpriced anyway. ..
According to market laws, it was "too cheap." A scarce market with high demand (Economics 1st semester) logically leads to higher prices.
Given the market situation, the variant "submission of written offers" would also make sense: Then the interested parties can name a price they are willing to pay. However, the rules and procedures for all parties involved would have to be clear from the start – especially the deadlines.
With a fixed defined selling price, it would be clear to me: The first person to sign the contract gets the house. Stalling is not an option.
And my experience from a few years ago, when we wanted to buy inventory (in B/C location, not Munich or anything), was that the one who looks solvent and brings 10K€ cash to the viewing appointment wins. And of course additionally pays the listed price.