"This tea tastes bad."
Correct. まずい at its core means tasteless and can be used additionally in situations where what is being said is tasteless or a situation which is grim. As regards taste of food, however, まずい would generally refer to either bland food or food without a flavor that one appreciates favorably.
So I'm using Microsoft IME for typing hiragana and kanji. I cannot figure out what I have to type in to get the small や。I type "ochiya" and I get おちや。If I type "ochya", I get this - おｃひゃ
Ocha or ocya or otya. The small や forms a contraction, so there would be no 'i' in the sound.
While there are a few different methods for character entry and use of roman characters to represent Japanese words, the Hepburn Style is becoming more standard.
Just a tip: you might wanna redo the first lessons where duo teaches hiragana, because it shows a lot of romaji when introducing the characters, such as ocha for small ゃ, kyo for small ょ, kyu for small ゅ and natto for small っ, and the same for katakana, so you can get used to what to type when you need them.