Possible pathways for the carbon present in plant material eaten by gorillas:
1) Released as CO2: The carbon in the food source will be oxidized during respiration and will convert to carbon dioxide. This process is also accompanied by the release of energy.
However not all the carbon will be completely oxidized.
2) Converted to biomass through anabolism: Part of the carbon present in the food source will be used in the process of anabolism that generates biomass (helps us put on weight and also makes molecules necessary for the body's sustenance). This happens through the formation of intermediate metabolites (part of catabolism), which are used by the body to form more complex molecules containing carbon, nitrogen, oxygen, etc. (fatty acids, for example).
For more details of metabolic cycles, please search online. Wikipedia has excellent information on detailed pathways. Here only the basics have been summarized.
Part 2: The water cycle in your particular case will follow these steps:
Evaporation (from ocean surface)---> Condensation (of vapors to form clouds)------> Precipitation (in the form of rain).
Hope this helps. Good luck.