1) say and tell are very similar. And you can use either for the same situation and it will work. However in my opinion tell is more specific. For example 'I have a car, i need to tell john' would be used instead of 'i have a car, i need to say it to john'. Using say for something so specific wont make sense. 2) yes, unfortunately english has many other words that spell the same but are pronounced different, like heard and beard, and done and gone. Once you understand which is which you will be fine. I am native and i dont know why they are different...they just are! 3) they are not the same, put is either future tense (i will put the light on) or the past tense (i have put the light on). However when in present tense you use the word 'putting' (i am putting the light on. I am putting my coat on). Hope that helped