There are usually multiple strategies to successfully completing a scenario; these can be discussed on the scenario's discussion page or written down in an existing or additional section of this article.
Finish the wooden coaster first, as it is the least maneuverable. Build some small attractions, add necessities, hire staff and open the park. Then start building the other roller coasters. They can be as short as you want. Note that two of them allow a launched start, which can save you a lot of room!
Max out the loan and you can complete this scenario very quickly.