Can I do speech to text converting with arduino?
There are many Arduino type boards.  Some, like the galileo from Intel, are very powerful.  And are more expensive than the basic Arduino Uno.  It may be possible to program such a board for speech to text conversion.  But it is arguable that using a modern laptop with built in features (microphone, keyboard, display, speaker, ect) would make the task easier.

Also, consider current industry standards.  Many text to speech applications are now centered around cloud computing.  Think of Siri, Alexa and Cortana.  But even if you do, consider that the Arduino Uno only contains enough RAM to record an "utterance" of speech. On the order of a second, maybe two.

Finally, consider COTS (Common Off The Shelf) parts (Arduino shields).  Searching "arduino speech to text" I found at least one device.