Is there a place where we can rent beach umbrellas? Also, we want to explore the island so is it possible to rent scooter or ATV? We’re staying in Limenaria.
Hey cvmarija! 
In Limenaria, you can rent a scooter or ATV from Motozagos! They are very reliable and have competitive prices.
https://www.go-thassos.gr/visiting-thassos/transportation/motozagos?anchor=node-1401
For beach umbrellas, you will need to buy one from a shop or supermarket or borrow from your host if they have one to lend you. Otherwise, there are many well-organized beaches on the island that provide sunbeds and umbrellas usually with the purchase of a drink.