Welome to OSM! For trails which are closed to the public, please don't delete them - someone will most likely come back and readd them. Instead, you can use access tagging to clearly indicate that they are not open to the public. Wiki article for reference and further explanation: https://wiki.openstreetmap.org/wiki/Why_can%27t_I_delete_this_trail%3F

Happy to chat further if you have any other questions!