Salesforce can be easy to learn if you focus everyday towards learning one specific thing.
Where people get stuck at is trying to learn 2 or 3 things all at one time.
If you’re studying to be a Marketing Cloud Email Specialist, then that needs to be the ONLY thing you study and learn. Everything else can wait until you get that 1 certification you’re studying for.
As for what to use:
Go to Trailhead.salesforce.com and Help.salesforce.com to learn salesforce.
Trailhead is a fun place to learn salesforce with hundreds of badges you can earn and real world projects (called superbadges) you can do.
Help.salesforce.com is the official documentation place you can use if you want to learn more in depth material on how to do something specific in Salesforce.
Do you think Salesforce is difficult to learn?
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