Click on the crown icon (top right on the main screen). Click on 'Upgrade to Pro Now'. A purchase dialog from Google will appear. Please enter your Google payment information. You will get lifetime access to all content and features.
When you change to a new Android phone or tablet, you will still have your access if you log in with the same Google account. Please note that the Pro version can not be transferred between Android and iOS devices.
Please send us the sentence and correction. You can do so by opening the sentence in the app. Then, tap on the flag icon (top right) and select 'Submit Report'. A screenshot will be created automatically and attached to your email. We will take a look at the translation and will launch a fix in the next update. Thanks for your support.