Don't worry, we've thought out this process for all levels of learners. 😉
First, we provide "hints" for new sentences. If you're learning Arabic, Russian, Chinese, or Japanese, your hints will always be romanized. This is just to help you get familiar with the phonemic string of sounds, as they are written in that language. In the case of Chinese, it is just the standard pinyin spelling, which is an accurate representation of the pronunciation. This process of typing will carry over when you start using a native keyboard, so your input in romanization will also match how you type directly in the foreign script.
Second, for European languages that have lots of diacritics, like á â à ä, we actually accept the base letters too! We know that you want to enter your answer as quickly and easily as possible, and we believe that through enough exposure you will also know the correct diacritics for every word, just as a native speaker knows them, but it takes time and we don't want to force-feed you. On the other hand, you can choose to be tough on yourself and input every letter correctly. This is your decision, so the ball's in your court!
Additional tips: punctuation is optional, capitalization is optional in every language, spacing is optional in Japanese, Chinese, and Thai.