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Hey there, PD
You do have the Microsoft learn modules that you are able to use: https://learn.microsoft.com/en-gb/azure/?product=popular
Unfortunately, there is no sandbox environments anymore, so it will mean you would need to use a pay as you go subscription and get charged for the resources you have used. Initially, the pay as you go subscription doesn't charge you until you have started using resources that generate a cost.
As you have already used your free trial account, you won't be able to sign up for the free trial again.
In terms of other sites that offer guidance and training. I am unaware of sites that exist. However, there may be in person training offered by universities and collages.
Hope this helps,
Nathan