~도 usage
~도 is a particle that translated into “too”. 도 can replace either the subject (는/은) and object (를/을) particles depending on where it’s placed. 도’s placement depends on what you’re saying ‘too’ to.
나도 한국어를 말해 → I speak Korean too (in addition to other people) ↳ Here, 도 is attached to 나 (the informal way how to say ‘I’ and is also the subject of the sentence). So because of this, it’s saying ‘too’ to the other people. Like when you’re introducing yourself and someone says “I speak Korean”, then you could say this (with the formal version of course).
나는 한국어도 말해 → I speak Korean too (in addition to other languages) ↳ Here, 도 is attached to 한국어 (meaning the ‘Korean language’). So because of this, it’s saying ‘too’ to other languages that you speak. Like when you’re saying how many languages you speak and you say this in addition to other languages.