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Are these sentences correct ? If not, would you correct them ?

#1 I solemny swear to protect my nation under God, for liberty and justice.

#2 I am shameful of myself being cowardice.

#3 I felt shameful after I cheated her twice.

#4 I feel more masculine if I exercise more.

#5 It would not have made a difference to me if they had not watched the movie at the schedule what they had planned.

#6 On Jay's new record, he did not sing well

#7 Unlike the city, the county I visited has no building.

#8 I compared the city where I live that has full of beautiful, impressive, magnificent and tall buildings to the county where I visited last Sunday that has small and big houses disguised by long and big trees everywhere.
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#1 I solemny swear to protect my nation under God, for liberty and justice. (solemnly. isn't this the USA pledge of allegiance? Inchoate's suggestion makes more sense for 'real' speech)

#2 I am shameful of myself being cowardice. I am ashamed of myself for being a coward. I am ashamed of my cowardice. Inchoate's suggestion incorrect.

#3 I felt shameful after I cheated her twice. I felt ashamed after I cheated her twice. Do you mean cheated, which could refer to all sorts of cheating, or 'cheated on', which only refers to adultory type situations?

#4 I feel more masculine if I exercise more. ok. Inchoates suggestion also ok, slightly different meaning.

#5 It would not have made a difference to me if they had not watched the movie at the schedule what they had planned. Inchoate's suggestion is incorrect. Try 'watched the movie at the time they had planned' or 'watched the movie according to the schedule they had planned'.

#6 On Jay's new record, he did not sing well .ok, or without the comma.

#7 Unlike the city, the county I visited has no building. do you mean countryside instead of county? building is incorrect here. Do you mean it literally has no buildings (plural) or were you referring to building as a verb - or to mean a construction industry. You will need to rephrase it to make your meaning clear.

#8 I compared the city where I live that has full of beautiful, impressive, magnificent and tall buildings to the county where I visited last Sunday that has small and big houses disguised by long and big trees everywhere. I compared the city where I live - full of magnificent buildings - to the country(? countryside?) I visited last Sunday, which only has (why also mention big as that destroys the element of comparison with the city) small houses hidden behind tall trees.
Comments  
I felt shame for being cowardice. Yours is faulty.
I solemnly swear to protect my country in the name of God, to maintain/attain liberty and justice.
I felt shameful after I cheated her twice. It is ok.
The more exercises I do the more masculine I feel
5#:... the movie what they had planned before.
6# No comma and period.
7#Ok.
8#I compared the city where I live -- it has many magnificient,, impressive, beautiful, and tall buildings -- to the country I visited last Sunday, where there is either small and big houses hidden by big trees aligned alongside the streets.

In my opinion, mind!

Incho
 nona the brit's reply was promoted to an answer.