You need a visa to travel to Senegal. You can apply through Visa Senegal.
You should avoid road travel in the Casamance region to the west of Kolda, other than in daylight hours on the main road from Ziguinchor to Cap Skirring and the main road north of the Guinea-Bissau/Senegal border from Sao Domingos to Ziguinchor. See Local travel
Most visits to Senegal are trouble-free.
There is an underlying threat from terrorism. See Terrorism
Take out comprehensive travel and medical insurance before you travel.