Nick here from Shopify.
I'm not completely familiar with Fruugo as a marketplace. It does seem safe and legitimate from their website here, but in terms of how simple it is, I'm not 100%. Something else to note is that it might be country dependent on if you can use Fruugo or not. I took a look at the Sales channels apps in the Shopify App store here and I didn't see one for Fruugo, so again I'm not sure if it's compatible with Shopify also.
It could be worth reaching out to Fruugo directly here and doing some research on them to see if you are comfortable with it and feel like it's something easy to use.
Are there any other marketplace options you'd be open to using or do you specifically want to work with Fruugo in this instance?
All the best, Nick