In case you recognize mould around the window sill or frame, deal with it first. Cover the wall and ground underneath the window by using a plastic fall cloth. You could thoroughly clean nonporous surfaces with cleaning merchandise, moderate dish detergent and water or a solution of water and bleach https://dailyspecter.com/achieve-spotless-surfaces-with-pure-water-cleaning-the-ultimate-solution-for-window-and-building-cleaning/