Excel spreadsheet very slow in Excel 2016

Hello, I have a spreadsheet that runs fast in Excel 2010, but very slow in Excel 2016. I was not the person who created the spreadsheet but I have to get this spreadsheet to run fast in Excel 2016. The issue is when a value is changed in a cell a series of Formulas get updated. While this happens Excel 2016 states its "unresponsive" for about 60 seconds. Additionally we see the memory consumption spike. If you save and exit the spreadsheet and then go back into the spreadsheet the memory consumption goes back to normal. I need someone who is VERY good at Excel formulas. We are looking for someone to identify the issue and then fix it so the formulas run in less than 5 seconds. Perhaps there is a better way to write the Formulas? Ideally you would already have Excel 2016. If not, I can provide remote access to a PC that has Excel 2016 and the spreadsheet on it. Due to the confidential nature of the spreadsheet I unfortunately can not share the spreadsheet except with the winning bidder. Thanks