If at the first edition
don't use this word "edition", say "at the first staging", or better still,
"the first time the school took place"
insite -> insight
european -> European
we hope to reach a friendly atmosphere as in the past edition of the school
achieve previous staging
internationally renown experts
renowned
"programme" and "program" are used interchangeably; be consistent;
since you use US spelling elsewhere, stick with "program"
"accomodations" should be singular
partecipants -> participants
justificatory of payment -> proof of payment