You could try playing with gps.conf. I’ve had an improvement where the gps lock sometimes takes less than 20 seconds indoors in areas where it failed previously. Assuming GPS positioning and offline/online position locks are set in custom settings. Here is the config I used: gps.conf.
You could also try moving the phone, I’ve noticed that if the device is stationary(indoors) it will not get a lock. Here’s a demo for the improvement after changinggps.conf: https://imgur.com/a/EwW42uC