Yes, you will find many popular brands selling completed bridges. For beginners, purchasing the bridges is better than building them from scratch. Otherwise, there is a high chance that your bridge will break in half when the train passes over it. Likewise, it is also possible to purchase railway tunnels and tracks. But in either case, you have to build your scenery first to decide how many bridges and what type of bridges you require to complete the railway track. You will also need to make some adjustments to your landscaping in order to fit the bridges over it.