What would you suggest H&M management do to prevent others from leaving?

Give thanks and more praise for working hard to achieve store results. Visit stores more often and give at least 3 strengths and 3 opportunities. Support your teams when they need it !! Take away top 40 days and make it top 10 days.
Don’t send 20 emails a day

Be more strict with the hiring process (hiring experienced people created a better team). Always be friendly and supportive.

Manager need to give employees hours and they need to stop hiring more people while the loyal ones who have been working with them for 6+ months are left begging for more hours. A lot of time i see people leaving within 2 months of working with us just because of the hours. I hate seeing that because H&M is a great work place.

Stop hiring externally.

Nothing they are awesome

If staff would be able to bond more to enjoy their time in the store. If management would provide a clear ladder for career growth or learning potentials.

Motivate and inspire, stop hovering over employee's who have been working hard and are good at what they do - they can manage themselves. Get with the times, cutting back hours and never giving a raise is preposterous. No wonder there's a revolving door! Get rid of the lazy people and reward the hard workers!!!!