No -ed pattern, memorize the forms
Irregular verbs do not follow a pattern like regular verbs (they do not use "-ed").
You need to memorize their past forms.
Quick tip: Irregular verbs change completely in past tense.
Was / Were depending on subject
The verb "to be" is special. It has two forms in the past:
was (I, he, she, it) / were (you, we, they)
Irregular verbs = change completely (go → went)
"To be" = was / were depending on the subject.