1.

Although contractions with am, is, and are are
commonly used, there are no contractions for
affirmative was or were:

I am ---> I'm
I was ---> no contraction

she is ---> she's
she was ---> no contraction

they are ---> they're
they were ---> no contraction

2.

Although there are no affirmative contractions for
was or were, negative contractions for these forms
of BE are very common:

I was not listening. --->
I wasn't listening.

She was not paying attention. --->
She wasn't paying attention.

They were not concentrating. --->
They weren't concentrating.

3.

Contractions with am, is, and are are commonly
used when the subject is a noun--especially when
the subject means he, she, or it, but there are no
contractions when was or were is used in this way:

Bob is sleeping. ---> Bob's sleeping.
Bob was sleeping. ---> no contraction

María is watching TV. ---> Maria's watching TV.
María was watching TV. ---> no contraction

The bell is ringing. ---> The bell's ringing.
The bell was ringing. ---> no contraction

4.

5.