Update/rewrite an older IOS pre-v8 app to IOS11 and ARKit

I have an older IOS app which was used to collect the start and finish times of boats during sailboat races, take a photo at the start of the race and as boats were finishing; and email or otherwise push the results and photos to a server. The app was complete, but buggy, and was not yet released. The developer has moved on some time ago. The app does the following: 1) create fleets - each group of racers is put into a 'fleet' with some details about their boat and their numeric handicap rating. Basically, a CSV, one line per boat, which is either filled out in the app, or can be uploaded from a file. A race will typically have multiple fleets, each having multiple boats in the fleet. 2) run a race - there is a 'start' button to start each 'fleet', with the option to take a photo at the start. The fleet's yachts are then 'racing' and a timer is capturing the racing time. The yachts typically will finish at separate times and a button is clicked on the app next to the yacht's name to capture the finish time. Optionally, a photo of the finish time can be taken. 3) view results - there is a separate function to view the results of the race. The race has simple math of the elapsed time +/- the boat's handicap per mile to determine the 'corrected time'; the boat with the lowest corrected time wins the fleet. This is simple spreadsheet stuff. 4) advanced - this screen has the setup to upload results / photos / etc to a server, website, or social media. It also has a few adjustments which can be made to the race scoring calculation (mentioned above). The app still builds and installs in IOS10 but crashes; it won't build on the latest Xcode. It last worked in IOS9 and was 90% functional. I'd like to update the code base to work with IOS11. Also, the photo-taking capability, which involved using a text overlay on the camera's viewfinder display, seems like a good use case to move to ARkit so I'd like that approach updated as well. I have the original design documentation and screen mock-ups along with functionality explanations which can be shared. Once this is working there are a lot of enhancements I'd like to add to the app going forward, but to start the baseline functionality is the goal. Some of the UI elements are 'old' and should be changed to support modern IOS 'normal' as well rather than retain custom functions.