To get contracts and successfully complete them, a freelancer needs to focus on their profile, portfolio, and proposals. Upwork has a "Resource corner" (at the top) >> 'freelancing resources', which includes informative discussions and webinars (recordings). Usually, those are helpful to craft competitive proposals and develop a strong portfolio or a well-written profile.
Although profile/portfolio does not guarantee any contracts, it considerably increases your chances to get one. Also ensure that your profile visibility is not 'private'. That will allow clients to invite you for jobs.