First of all thank you for the reply and advice. I think you will understand the dilemma we are facing after I answer your questions:

So you are looking for a developer who can build a crypto exchange for IOS and Android?
Yes. Preferably a team/company that has blockchain and mobile development experience.

Since you want it to finish in a short time I think much better to find a crypto exchange developer/expert on Upwork. Which is one of the best places to find developers who can build Crypto exchange for IOS and Android devices?
(a) Timeline, I would be ok using a white label solution, but I cannot find a single company offering such a product for mobile. Either Android or iOS.
(b) I've looked on Upwork, was one of the first places I reviewed. Here's the issue: Building from scratch is a pretty hefty development. I've interviewed more than a dozen teams and their competence level is typically limited or missing 1 or more important elements.

Also, check Fiverr I found some post who can build a crypto exchange for mobile phones. Just use a keyword "crypto exchange"
Yeah, I tried Fiverr as well. Feedback: Fiverr is just funny for this level of a request))) The competency level here is typically very narrow to something that the person offering services is very competent in doing. Certainly not building a FinTech application for what we hope will be millions of users and support over 20 cryptonodes.