can't automatically execute the formula

hello, can somebody else help me with this problem?

i'm currently using excel 2016 and there is my problem

at cell B6 I type "rabbit", B7 = "dog", B8 = "frog"

I go to cell C6 using this formula "="B6" then it shows "rabbit"

then i drag it down to C8, but the outcomes for C7 and C8 is "rabbit" i'm not using lock cell at formula ($B$7)

i go to cell C7, i press F2 then enter it change into "dog" same as at cell C8. the formula I used doesn't execute automatically.

please help me to fix it. maybe it does problem with my settings at Excel.

it does work automatically with your suggest. thank you so much