I onw star flight 1 & 2, but i got a new computer is there any way i can get the games install on my new computer, or i have to buy it .

What do you mean, if you log into your gog account, the games should be in your library that you purchased.

You can use your computer browser (Firefox, Edge, Chrome or whatever you use) to download the games as many times as you want.
In your browser go to gog.com website and log with your username password. After login go to your account -> games -> Starflight -> download offline installers (ignore the big blue button).

Alternatively you can click the big blue button and install Galaxy launcher as well (not needed to install and play the game but maybe needed to access the cloud saves).

Edit: Print addded for reference

Yes. No.