The portal tracks are for the mines/foundries to connect to the dwarven portal, but it looks like you've left Dwarves and entered fairies (I see the fairy portal in your city). As long as you've already completed the 'remove dwarven portal' quest, you can also remove the mines/foundries to make room for the fairies settlement. You'll get new fairy settlement connectors that work like the portal tracks (flower lanes) and connect the day and night farms to the fairy portal. The portal will need a regular street connection to the main hall just like the dwarven portal did.
Dwarven streets are just like your other regular streets, but with higher culture than your last chapter roads. You won't need dwarven goods any longer except to build more regular Dwarven streets. You might want to stock up on the granite/copper to build those streets before selling everything off, but you'll need to connect them to the dwarven portal with portal tracks for them to work. If that's just too much trouble, make note of how much granite/copper you have (click on the dwarven portal) and you can use it for more dwarven streets even after you sell off the portal. You just won't be able to see your granite/copper inventory after the portal is gone. At the end of fairies, you'll get your next regular streets upgrade (blossom street) and you can upgrade to those instead if you just want to wait.