1 - is good 2 - First sentence: "I own up!" is not very common - try "I confess" instead. 2 - Second sentence: "It was I who broke the lamp", or "I broke the lamp" 3 - looks ok. Maybe use 'had failed'.

Thanks to all of you, you've been of great help ! :)

Maria All 3 sentences are fine in English and you will be understood. As a phrasal verb to 'own up' is a slightly less formal kind of expression than to confess, In the second sentence you could say I broke the lamp, but 'it was me who broke the lamp' is perfectly correct informal English (see Michael Swan 'Practical English Usage' section 429. It was I who broke the lamp' is correct but very formal and in practice would be less common in spoken English than the form you have used. 'I failed the exam' (simple past tense) is perfectly OK in spoken English and is particularly common in American English. As Gabriel points out I had failed (or I'd failed) is probably more formally accurate since the past perfect tense is appropriate for actions described prior to other actions in the narrative, e.g 'I owned up to my mother that I had failed....

Hola Maria, es possivel contar con tu colaboracion para aprender espanol?

1- good 2- First sentence. Same as other commenter. "I own up" would only be used if a person was accused or in a group setting where one person is trying to see whom is the guilty person. 2- Second Sentence- good as is for normal colloquial (American) English. 3. Looks good