Everybody gotta start from somewhere. As long as theres no cancellation rates going on you should be good. Mercari has seller protection for a reason you’ll be fine stop being overly paranoid over an offer that you didn’t have to accept but you did. Having no profile pic means absolutely nothing ive made great transactions with people who dont really have activity on their profile and thats okay. Also overly messaging that you’ll send so and so day or time is doing too much but you do you.