Well, I found a similar topic in the forum regarding using ancient languages / "dead" languages in your practice. Theurgy supports this approach, believes it is important, and empowers your casting, calling, and rituals... You will find a division in opinions and thoughts regarding using ancient/"dead" languages. Personally, I think it is more important the intention and energy you invest, rather than the language. However, I also believe that if you are following a tradition and if the knowledge has been passed down using another language, then you should use it.
If you are not comfortable with that language, but want to preserve the traditional approach of your practice, then I suggest study the text and at least learn to say the key words in that text, or in this case in the Orphic Hymn, learn their meaning and how to pronounce those key words, so those words when you proclaim have power, intention and work as bridges between the past and the present. For example, in my practice, when I connect with my deities, I use a greeting in the Yoruba language; the rest can be in my native language, but the greeting and invocation are always in Yoruba. So let's say you are using the Orphic Hymns to connect with a certain Greek Pantheon deity; I would try at least to know how to say their name and key elements connected to them in that language.