Romanian past tense is different from Present because you are required to use pronouns to indicate who is doing the action. This is because the verb itself does not conjugate and therefore the pronoun is required to.
You may have noticed that the pronouns are nearly identical to the conjugated forms of 'have/has' in Romanian. Keep this in mind when memorizing.
Above 'Merge' (s/he goes) has been modified for the past tense. Notice how the 'S' ending is used.
Above 'Spune' (s/he speaks) has been modified for the past tense. Again, notice the replacement of the final consonants with an 'S'.
Above 'Face' (s/he does) has been modified for the past tense. See here how, like the other examples the final consonant has been replaced. This makes no sense on paper, as on it paper it hasn't changed. 'C' is 'C'. But it has changed in pronunciation. Rather than being pronounced as 'Fachay', it is pronounced as 'Fuhkoot'. This is a result of the letter 'C' having two alternative sounds in Romanian (it is the only letter to do so). The difference between this example and the other two is that instead of an 'S' at the end, there is a 'T'. Both 'S' and 'T' are used for the Romanian past tense, so when you come across a new vowel, make sure to know if the past tense ends in an 'S' or a 'T'.