The first thing you should do is to buy a strip of land so that you can connect the two sections of the park separated by the river. The roller coasters in the sea-themed area can help attract guests to your park, so it is a good idea to connect the park to the rides as soon as possible. The sea-themed area contains multiple footpaths around the area, many of which duplicate each other. It is a good idea to consider which are not necessary and demolish them. This will prevent guests from getting lost and generate more money for you. Also, demolish the Mini Golf and you can then use that space for another ride that will attract more guests to the park. You have 5 years to do this, so it will not be too hard. If you feel like you are not generating enough guests, you can advertise to help you reach the scenario objective. As this is a park that charges entrance rather than per ride, it is a good idea to add an On-Ride Photo Section to the roller coasters where you can to generate more income.
Don't worry about the other park at all! Sell the rides, stalls, scenery, and footpaths for extra cash, then build up your park. Five years is a long, long time. Advertise as needed, and keep your rides exciting and fresh. This should not be a problem at all.