I have written my essay yesterday
AND
I was writing my essay yesterday


The distinction is that the first sentence says I have completed the essay, while the second only states that I was doing it and probably didn't complete it

Translation into Russian:
Ja napisal moj esse vcxera
I
Ja pisal moj esse vcxera

JA ZUPISAL MOI ESE VCXERA.
(I have written and completed my essay yesterday)

MOI ESE BIL ZUPISALJU VCXERA.
(My essay was written and completed yesterday)

JA PISAL MOI ESE VCXERA.
(I was writing my essay yesterday)

JA BIL PISATSJU MOI ESE VCXERA.
(I was writing my essay yesterday)

MOI ESE BIL PISATJU VCXERA.
(My essay was been written yesterday)
============================================

Slovio can be even more exact than english and express many other nuances of the sentences above, in a concise and precise manner.

Ja cxital, zxe ti domovijsx vo Kalifornia. Ktor grod ti domovijsx? Ja domovijm vo Costa Mesa, to es jugju Kalifornia.

Ja domovijm vo Sunnyvale

Pozdrav dla Slovianis vo Sunnyvale i San Francisco od Slovianis iz Los Angeles i Orange County!