Praying in a mosque which is attached to a grave in the direction of the Qiblah

It is not permissible to pray in this mosque that is
adjoining the grave, especially since the grave is in the qiblah faced by the worshippers,
and between them there is a wall with windows in it that overlook the grave. It is still
not permissible even if it does not occur to them to venerate the grave. It was reported
that it is forbidden to pray in graveyards. ‘Umar saw a man praying at a grave and
forbade him to do that, saying, ‘Don’t pray at the grave.’

(Narrated
by al-Bayhaqi, 2/435; classified as mu’aalaq by al-Bukhaari in his Saheeh,
1/523; classified as mawsool by ‘Abd al-Razzaaq, 1/404, no. 1581).

On this basis, you have to move the mosque to another
place, or enclose the grave with a separate fence that will form a barrier between it and
the wall of the mosque. And Allaah knows best.