barzahlen.rb

result = {}

slips.each do |k,v|
  key = k.split('_').last
  data = {}
  data[:number_transactions] = v[:transactions].count
  data[:shop] = Hash[*shops.flatten][v[:shop]]

  data[:total_amount] = 0
  transactions.select{|transaction| v[:transactions].include? transaction[:id] }.each do |transaction|
    transaction[:payout] ? data[:total_amount] += transaction[:amount] : data[:total_amount] -= transaction[:amount]
  end
  result[key.to_i] = data
end

puts results