UPDATE of several columns using SELECT statement

Hello,

I am facing the following problem, nothing tough, I guess (hope)….think it should be some syntactical problem:

1. When trying to update two columns

UPDATE myFirstTable SET (fistCol, secCol) = (  SELECT anotherFistCol, anotherSecondCol FROM mySecondTable )

I am getting: ERROR:  syntax error at or near "select"

2. When changed to (only the parentheses are changed):

UPDATE myFirstTable SET (fistCol, secCol) = ((  SELECT anotherFistCol, anotherSecondCol FROM mySecondTable ))

I am getting: ERROR:  number of columns does not match number of values

Does anybody know, what I am doing wrong? Thank you very much and wish you a luxurious day

Adam