Need an App UX/UI Design ASAP

We own a data aggregation company, we simply need a Professional front-end (UX/UI work) that’ll be sleek, modern, and convenient to use. The UX UI should be fully functional and able to be tested by installation on its own, where we’ll need to test its functionality before our in-house devs work on all the services that’ll be behind it, then freelance will likely be hired for back-end pointing.
We have a site for color palette and logos to draw from, otherwise the freelancer has the freedom to make whatever stylistic choices they deem fit for the project.