Most of Suriname is forest. You do not have to go far from Paramaribo to stand under trees: Cola Creek and Berg en Dal do that in a day. Brownsberg is the next step, with a plateau, trails, and the reservoir below. The Upper Suriname and the Central Suriname Nature Reserve are where the forest becomes the whole trip.
Howler monkeys are the sound people remember. Birds are everywhere and patient looking helps more than a long species list in a guidebook. Caimans live in the rivers. See them from the boat. Do not approach them for a photograph.
Trails can be muddy, steep, and poorly marked after rain. A local guide is not a luxury on Brownsberg or on any interior walk. Tell someone where you are going and when you expect to be back.
While you are there
Do not feed animals, and do not take plants, feathers, or seeds. Stay on the path your guide is using. A drone over a village or a nesting beach is not a souvenir.