I want to do sukhmani sahib path for 40 days. But I fear doing it wrong because I don’t know Gurmukhi. What should I do?

Doing Path 40 or 101 days without understanding is meaningless and anti Gurmat.
ਪੜਿ ਪੜਿ ਗਡੀ ਲਦੀਅਹਿ ਪੜਿ ਪੜਿ ਭਰੀਅਹਿ ਸਾਥ ॥ ਪੜਿ ਪੜਿ ਬੇੜੀ ਪਾਈਐ ਪੜਿ ਪੜਿ ਗਡੀਅਹਿ ਖਾਤ ॥ AGGS 467
Parr Parr Gaddi Ladheah Parr Parr Bhareah Sath || Parr Parr Berri Paeai Parr Parr Gadeah Khat ||
ਪੜੀਅਹਿ ਜੇਤੇ ਬਰਸ ਬਰਸ ਪੜੀਅਹਿ ਜੇਤੇ ਮਾਸ ॥ ਪੜੀਐ ਜੇਤੀ ਆਰਜਾ ਪੜੀਅਹਿ ਜੇਤੇ ਸਾਸ ॥ ਨਾਨਕ ਲੇਖੈ ਇਕ ਗਲ ਹੋਰੁ ਹਉਮੈ ਝਖਣਾ ਝਾਖ ॥੧॥
Parreah Jete Baras Baras Parreah Jete Mas || Parrea Jeti Aarja Parreah Jete Sas || Nanak Lekhai Ek Gal Hor Houmai Jhakhna Jhakh ||1||
We may read and read loads of books; we may read and study vast multitudes of books. We may read and read boat-loads of books; we may read and read and fill pits with them. We may read them year after year; we may read them many months there are. We may read them all our life; we may read them with every breath. Nanak says, only one thing is of any account, which is, getting knowledge and wisdom from them; everything else is useless babbling and idle talk in ego. That means reading Guru Granth Sahib without understanding and getting knowledge is meaningless.
So do Path slowly, may be one Shabd in a day but with understanding and then applying it on yourself which will change your thought process is meaningful.