No. Gambia doesn't ask visitors to fill in an online arrival form (also called an entry form, immigration card or landing card) before they travel. An airport security fee is paid at kiosks at Banjul airport.
Do I still need a visa for Gambia?
An arrival form is not a visa. Whether you need a visa or an electronic travel authorization depends on your nationality, so check Gambia's official immigration website or your own government's travel advice.