New to T-Mobile Home Internet today and getting really slow speed - help? advice?

Hi, all. Just got my NOK5G21 gateway today and was super excited to get started. No matter where I go in the house, I only get two bars. I have not been able to speed test above 4Mbps download or 2Mbps up. I sent a support request email through the mobile app to T-Mobile but I just found this community and thought I would check here. I am not very tech savvy, so some of the posts I've seen are kind of intimidating. I am not sure I would know where the towers are or any of the stuff about some of these booster antennas. I saw that someone said leave it run for a while and speed will improve? If anyone has some info to share, please do. I'd hate to have to keep my Comcast service! Thanks :)