update concrete5

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Hi Team,
I am new to concrete5, I was trying to update existing website from 5.6.0 to 5.6.3.5 through Dashboard but when i click on install concrete5 gives me 500 internal error.
latest version is downloaded in /updates folder but while installing it has same problem.
I have also tried through manually putting updated file in /updates folder but still it gives me same error. Website has its own theme .

Thanks in advance