Good quality English translations of Sri Guru Granth Sahib ji are very rare, if any. In any case, the words of Brahmgyanis (People who are in tune with the Celestial Formless Creator) can be understood completely only by Brahmgyanis. It is like asking someone who has never seen an elephant, but only read about it, to describe how an elephant looks like. However, your spiritual journey needs a starting point. For me, this has always been kathas (spoken discourse) of Giani Maskeen ji, or the Punjabi translation of Sri Guru Granth Sahib ji by Prof. Sahib Singh ji.
Please find attached interpretations of the Sukhmani Sahib (one of the many prayers withing Sri Guru Granth Sahib ji) in English. This commentary pulls out key thoughts from the Sukhmani Sahib and tries to explain. This is work in progress, only a short part completed so far.