We don't have [g] in Vietnamese so I use [ɣ] instead. I wonder if it is acceptable since I can't tell the difference between them. And it seems like that native speakers can't distinguish the voiceless pair, because I saw people use [k] voiceless velar stop for [x]voiceless velar fricative when pronouncing foreign words.
First rule of English is that nobody in their right mind care about phonetics.
Second is that mistakes are a part of life, and overly clear, especially well articulated and grammar immaculate sentences are used by NNEs - as strange as that may sound.
So, if you can pass that however you pronounce it, and don't get really bad stares, it's all good. Carry on.