Lock a sheet from updating in between form submissions?

I have created a script on google sheets App script that will take a form submission, and put it into a new sheet. The way it does this is by calling on the last row with data, but when two forms are submitted at the same time, only one is submitted as the first did not have enough time to go through. Is there a way to still keep google forms open and delay the responses from updating the spreadsheet by 5 or so second intervals? I don't want data to be missed if two forms submit at the same time. Any help is appreciated as I am a COMPLETE beginner.