“Build up” is C1 in the English Vocabulary profile and B2 in the English Grammar Profile.
build (sth) up or build up (sth)
C1 to increase or develop, or to make something increase or develop
Dictionary examples:
This will help to build up his confidence.
Traffic usually builds up in the late afternoon.
Cambridge Learner Corpus Learner example:
What might take a long time to build up could be ruined in a very short time.
However this is used in the example to illustrate a B2:
57 VERBS phrasal B2 3 FORM: VERB + PARTICLE + OBJECT wide range of phrasal verbs + particle + object.
I don’t need to use my imagination while I’m surfing the internet, but if I’m reading a book I can build up the whole surroundings and the characters in my own head.
“Can’t Stand VERBING” is both B1 and B2
can’t stand sb/sth
B1 INFORMAL to hate someone or something
Dictionary examples:
I can’t stand him.
She can’t stand doing housework.
Cambridge Learner Corpus Learner example:
I can’t stand crowded shops.
56 patterns B2 2 FORM: VERB + ‘-ING’ FORM Can use an increasing range of verbs followed by an ‘-ing’ form.
we can’t avoid using them because we are used to them.