Bash scripting | Linux | if else statement [closed]

I'm having a bash script and it includes few config commands.

For example,

Command1 Command2 Command3 Command4 and so on...

The first time when the script is run, all the commands (Suppose there are 10 commands in that script) in that script should get executed. But after the first time, when the script get executed, only one command should get executed (For example, command5 only). How can I do this? Can I use "if statement" here? And how?