Open Office If Else funktion for two columns

I try to check the value of one cell to get a value for teh second cell in a other column. if B1 is '0' than i want in C1 also '0' and if B1 is '1' than i need to get in C1 30 (or at least greater than 1). But it downs't work.

I try

=if(B1=0;C1=0;30)

and get 'False'

and with

=if(B1>1;C1>1;30)

or

=IF(BJ1=0;BI1=0;30)

i get 30 but i need 0 in this case.

How can i make it working?