Question: My Hebrew isn’t great and I don’t understand most of the davening. Is it better for me to daven in Hebrew or in English?
Answer: There is a machlokes in the Gemara (Berachos 13a) as to whether shema must be recited in lashon hakodesh or if it can be read in any language. Rambam (Keriyas Shema 2:10) and the Shulchan Aruch (OC 62:2) pasken that one can recite it in any language providing they pronounce the words clearly.
Likewise, one may, if necessary, daven the amida in any language (Sotah 32a; Shulchan Aruch OC 101:4).
Tosafos (Sotah 32a) writes that one who doesn’t understand what they’re saying when they’re davening or reciting the shema has not fulfilled their obligation. They should rather recite it in a different language that they do understand. The Magen Avraham (OC 62:1; 101:5) and Pri Megadim (Eishel Avraham 62:1) pasken like Tosafos though the consensus of poskim is that it is certainly preferable to daven in lashon hakodesh even when they don’t understand the meaning.
The Mishna Berura (101:13) quotes the Chasam Sofer (84; 86) who demonstrates that one may only daven in a foreign language as a temporary measure. Elsewhere (62:3) he explains that as there are certain words that can’t properly be translated, such as veshinantam or totafos in the shema, one should stick to lashon hakodesh as much as possible (See Biur Halacha 62; 101). The Aruch Hashulchan (OC 62:4; 101:9; 185:3) writes that even the names of Hashem can’t properly be translated, and one mustn’t therefore, daven in a foreign language.
Nonetheless, R’ Moshe Feinstein (Igros Moshe OC 4:70:4) writes that if necessary, one may daven in English, though they must ensure to only use a good translation (See Rivevos Ephraim 3:92; 4:44:34).
In conclusion, it is certainly preferable to daven in the original lashon hakodesh even if one doesn’t understand the words. It is certainly best if one uses a siddur with translation so that they can understand what they’re saying.