So many things can go wrong with this project including th delay in your code with which you read data from the gps, the logic you’ve implemented to extract data from the gps, your lcd initialization and data writing code etc. Note that not all gps module communicate with same data stream. Some changes might be required in the code for extracting the required data. Make sure that you’ve used the same module for which the code has been written for.
Also check your circuit connections thoroughly, especially the lcd data lines. Are you getting anything on the lcd or simply black boxes?