How to change "until loop" to" while loop"

def raw_status
    timer = 5
end

def medium_status
    timer = 10
end

def well_done_status
    timer = 15
end

def process(default_parameter)
    start_time = 0
    until start_time >= default_parameter do
        puts "Preparing your meal"
        start_time += 1
    end
    p "Your steak is ready"
    end_phase
end

def start_phase
    p "Please select timer for your steak"
    timer = gets.chomp.downcase
    until (timer == "raw_status" || timer == "medium_status" || timer == "well_done_status") do
        puts "System caot recognize your command. Please select from these three options 'raw_status', 'medium_status' or 'well_done_status."
        timer = gets.chomp.downcase
    end

    if timer == "raw_status"
        process(raw_status)

    elsif timer == "medium_status"
        process(medium_status) 

    else timer == "well_done_status"
        process(well_done_status)
   end
end

def end_phase
    p "Would you like another steak?"

answer = gets.chomp.downcase
until (answer == "yes" || answer == "no")
    puts "Please key in yes or no"
    answer = gets.chomp.downcase
end

if answer == "yes"
    start_phase
else answer == "no"
    puts "System shutting down... Enjoy your meal."
end
end

start_phase