By Toby Cudworth West Ham United are closing in on the signing of Palmeiras teenager Luis Guilherme, sources have told 90min. The Hammers have already made their first major move of the summer, appointing Julen Lopetegui as their new head coach, and are now working hard to make 18-year-old Guilherme their first player signing. A deal worth €30m has been agreed with Palmeiras – €25m in guaranteed money plus a further €5m in bonues – and technical director Tim Steidten is currently in Brazil tying up the final stages of the move. Documents have already been created with the three-time Copa Liber…