You are absolutely right about Wojciech Szczęsny at Barcelona. He was only meant to be temporary fill in when Ter Stegen was hurt but his amazing performance with 14 clean sheets in 30 games really impressed  club and earned him permanent contract. While it is unclear if he will be main goalkeeper or backup next season with Joan Garcia also joining most important thing is that Barcelona now has much stronger defense with multiple good goalkeepers which is great for their overall team strength.