What is the difference among the following two sentences?
- 我 去 吃飯
- 我 要 吃飯 了
According to my current knowledge, both translate to ''I am going to eat''.
我吃飯 = I eat dinner (meal)
我(去)吃飯 = I (go) eat dinner
我(要)吃飯 = I (have to/ want to) eat dinner
我(要)(去)吃飯 = I (have to/ want to) (go) eat dinner
You can add final particle '了' (indicate change of situation) to all the above examples :
我吃飯了 = I eat dinner (meal) now- 了 indicates situation change from not eating to eating
我(去)吃飯了 = I (go) eat dinner now- 了 indicates situation change from not going to going
我(要)吃飯了 = I (have to/ want to) eat dinner now - 了 indicates situation change from not have eat to have to eat
我(要)(去)吃飯了 = I (have to/ want to)(go) eat my dinner now - 了 indicates situation change from not have to go to have to go
去 + Action vs 要+Action+了
我看電影 = I watch movies
我(要)看電影 = I (have to/ want to) watch movies
我(去)看電影 = I (go) watch movies
我(要)(去)看電影了 = I (have to/ want to) (go) watch movies now- 了 indicates situation change from not going to going
我 去 吃飯 sounds that you will go somewhere(eg. A restaurant) to have an eat. The sentence is used in response to 你干什么去？，干嘛去？
我 要 吃飯 了 sounds like, you have your meal handy/ready and you are just about to eat it. Or it's time for me to eat. Or just simply I am going to eat. Basically, the sentence is used when you want to tell somebody you are going to have a meal.
我 去 吃飯 I'm going to get something to eat.
我 要 吃飯 了 I wanna get my teeth into something.
我 去食堂 吃飯 I'm going to the canteen to get something to eat.
我要吃午饭。I want some lunch.
You are correct, both can be translated as 'I am going to eat'. Yet "going" has completely different meanings in the two sentences.
The first one is "actually going / moving yourself to a place where you have food" and the second is "planning to, intending to have food".
This question is about ambiguity of English, not Chinese ;)
PS A better translation of the first phrase using "going" would be "I am going to have food / to a restaurant etc"
我去吃饭 literally means "I go to have my meal" because 去 can be translated as "go" in Chinese. 我要吃饭了 literally means "I am going to have my meal". And in some context, it can also mean "I must have my meal".
The first one sounds more like you have already known or planned what you are going to eat and now all you have to do is to eat it directly.
Q：You seem to be in a hurry. (你似乎急急忙忙的) What are you going to do? (你要去做什么？)
A：I go to have my dinner. (我去吃晚饭) I'm gonna be late. (我要迟到了)
The second one is more frequently used in the context that it's time to have a meal and you decide to eat it.
E.g. Sorry to interrupt you. But I have to take a leave. I'm going to have a meal. (抱歉打断你了，但是我得离开一会。我要吃饭了。)