folium_plot_lines.py

import gpxpy
import gpxpy.gpx
import folium

gpx_file = open('path_to_gpx_file.gpx', 'r')

gpx = gpxpy.parse(gpx_file)
points = []
for track in gpx.tracks:
    for segment in track.segments:        
        for point in segment.points:
            points.append(tuple([point.latitude, point.longitude]))
print(points)
ave_lat = sum(p[0] for p in points)/len(points)
ave_lon = sum(p[1] for p in points)/len(points)

# Load map centred on average coordinates
my_map = folium.Map(location=[ave_lat, ave_lon], zoom_start=14)

#add a markers
for each in points:  
    folium.Marker(each).add_to(my_map)

#fadd lines
folium.PolyLine(points, color="red", weight=2.5, opacity=1).add_to(my_map)

# Save map
my_map.save("./gpx_berlin_withmarker.html")

Hello @philshem recreate .csv and it works without any issue! thank you Angelo