fig, ax1 = plt.subplots( figsize= (20,8))

ax2 = ax1.twinx()
ax1.plot(df_cuba.wk_year, df_cuba.GP_per_sender, '-m')
ax2.plot(df_row.wk_year, df_row.GP_per_sender, '-k')


ax1.set_xlabel('X data')
ax1.set_ylabel('Y1 data', color='m')
ax2.set_ylabel('Y2 data', color='k')

plt.show()