the た ending.

While learning Japanese I have encountered some sentences that end in た

何て言ってた。

さっきせんぱいがおこりそうになってた。

このアニメはだんだんつまらなくなるって友だちが言ってた。

I asked a couple of Japanese but they just say that many past tenses end in a た。
And they give examples of regular conjugations
言った、買った、やった‥来た‥分かった、など。。。

I do see some structure ( the て gets a past form by adding た) but there is so much wrong with that in my mind that I won’t share to confuse other learners.

I have not encountered anything else than the ~てた。
At first I only had the “言ってた” endings but today ~そうになってた was added.