If you do not know Hebrew well enough to daven in Hebrew from the siddur, or your concentration/intention is better while davening in English, I understand that it is permissible to daven in English, or whatever your native language is. If you would like to daven in Hebrew while understanding the English better, the interlinear siddur can be good for that.
In addition to davening the formal prayers from the siddur, it is very beneficial to engage in at least a few minutes a day of personal prayer in your native language, thanking and praising G-d for everything, analyzing your deeds and doing teshuvah for your sins, and asking for whatever material or spiritual things you need. Some rabbis, such as Rebbe Nachman of Breslov, emphasized the importance of this practice, and recommended strongly that all people spend at least an hour a day doing this. The Essential Rebbe Nachman, available online for free, or the books of R’ Shalom Arush, are good sources of information on this practice.