If you’d like to try Things before you buy it, you can install the trial on your Mac.
A free and fully functional 15-day trial of Things is available for your Mac as a direct download. It requires macOS 10.13 High Sierra or later.
After 15 days, the trial version of Things will stop saving any new changes you make, but it will keep what you entered up to that point. You can then purchase Things to continue using the app.
Trials for other devices
At this time, only apps which require in-app purchases (IAP’s) or subscriptions can offer free iOS trials. Things doesn’t require IAP’s and is not a subscription – for that reason, Apple doesn’t offer us a way to let you try the iPhone or iPad app at this time.