it's a really easy tab
standard tuning EADG
verse
"you had my heart..." X2
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------------4-44-4-44-4-1-11-1-11-1-------------|
1-11-1-11-1-------------------------4-44-4-44-4-|
chorus
"...when the sun shines..." x2
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----------------44444444444444441111111111111111-----------------|
1111111111111111--------------------------------4444444444444444-|
[ Tab from: https://www.guitartabs.cc/tabs/r/rihanna/umbrella_btab.html ]
post-chorus x2
"...under my umbrella, ella, ella eh, eh..."
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------------44-44-44-44-11-11-11-11-------------|
11-11-11-11-------------------------44-44-44-44-|
reapeat
verse
chorus
post-chorus
bridge
"...you can run into my arms..."
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4-44-4-44-4-4-44-4-44-4-3-33-3-33-3-1-11-1-11-1-|
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4-44-4-44-4-4-44-4-44-4-3-33-3-33-3-4-4-4-4-4-4-4-4-|
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chorus
post-chorus
outro
"...it's raining..."
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-------------4-444-4-44-4-1-111-1-11-134-444-4-44-4-|
1-111-1-11-1----------------------------------------|
you can do what i did and added alot of fillers to it