For the first question, I'm not really sure about what "Wo Shi Chi De" means. We Chinese people wouldn't say that in this way. The second phrase is the exact one while the third, it usually is used to describe the fact that in the past you've had things like apples, bananas, peaches and the list goes on. For the second question, I would say " I Chi Tai Duo Le" or " I Le Hen Duo“ Hope it would be helpful.

Q1:If you want to express you ate ,"wo chi le ",represent it had been finished. Q2:"wo chi le yi ge ping guo"It is right .It is also expressing that you had ate an apple. Q3:If you wanna say that in pinyin ,you could say "wo yi jing chi le hen duo le " or "wo chi le tai duo " or "wo yi jing chi bao le " or "wo yi jing bao le " In fact ,there's too much ways to express your words in Chinese as same as in English . I hope that will be useful for you .

Q1: if you want to express: I ate, you can say: 'wo chi guo le.' or 'wo chi guo.'（我吃过了。or 我吃过。） wo chi le.（我吃了） and in your questions, 'wo shi chi de' means 'I am food' in Chinese,obviously it's not right. Q2:You want to know how to say a word in different tense,but you should know that strictly say Chinese grammar system is different with English,we could add some adv. or other words to convey different time. eg1. wo chi le yige pingguo. you could understand it means 'I ate an apple', which there has a word 'le' that usually means in the past in Chinese.BUT, in Chinese,the verb don't have to change ,so there are wrong sentences below: "wo chiing le yige pingguo" "wo have chied le yige pingguo" ... ... Although that, you can find the Chinese has another expressions if you wanna convey in different time. wo zheng zai chi yi ge ping guo. （我正在吃一个苹果）//I am eating an apple. wo deng hui hui chi yi ge ping guo.（我等会会吃一个苹果）// I will eat an apple for a while. if you wanna know more,maybe this page has more details: https://www.quora.com/Are-there-languages-that-don%C2%B4t-use-verb-tenses-to-express-the-concept-of-time-and-if-so-how-do-they-express-the-idea-of-time-past-present-and-future Q3:if you wanna express you have been eating so much,you could say: wo chi tai duo le.（我吃太多了） btw:if you are an English native speaker, you could correct my sentences if there are grammar mistakes or unsuitable expression in English.Thanks.

They are not all right .it just right the 2th is,shi and chi should not be used together, you should add le after the "guo".wo shi chi yige pingguo de is not correct ,you should get rid of the shi and de, it is should not use shi with adv in chinese .wo chiguo pingguo should be wo chiguo pingguo le.and the last ,it's wo chi tai duo le or wo chi le tai duo .that's my answer ,my English is not too well ,if you can't understand ,I'm looking forward your next question. you are welecome.

Thanks Jack!!