In Modern Dutch I do not see or hear any hard G sound. Garden would be pronounced like Harden.. how did that happen?
It is generally held that in proto-Germanic, [g] and [γ] are in an allophonic relation, likewise [b,d] and [β,ð], similar to the situation in Spanish. Word-initially, the stops [b,d] are posited as positional variants. However, the North Sea Germanic languages including Dutch maintained the fricative pronunciation [γ] initially, though other languages developed stops across the board. The fricative allophone was ultimately lost in English, but Dutch retained the fricative – thus Dutch preserved an older phonetic value for the voiced velar obstruent. That does not mean that there was no phonetic [g] in proto-Germanic, indeed it is assumed that the b,d,g were stops post-nasally.