Question: "Is it important to know Greek and Hebrew when studying the Bible?"
Answer: Martin Luther, the great Protestant reformer, wrote the following in regard to the importance of understanding Greek and Hebrew when studying the Scriptures: "The languages are the sheath in which the sword of the Spirit is contained." God sovereignly chose to have His Word written in Hebrew (the Old Testament) and Greek (the New Testament).
Our modern English translations are excellent. Most of the major English translations available today are superb renderings of the original Greek and Hebrew. However, in any translation, not everything that was communicated in the original language can be precisely conveyed in another language. Some nuances do not transfer well from one language to another. As a result, a translation rarely is a perfect rendering of the original. (This is one reason why the Amplified Version was published.)
An example of this is the "aspect" of Greek verbs. English verbs have tenses—past, present, and future. Greek verbs have these same tenses, but they also have what is known as "aspect." Present-tense Greek verbs mean more than the action is occurring presently. A Greek verb can also carry the meaning that the action is occurring continually or repeatedly. This is lost in English unless the aspect word "continually" or "repeatedly" is added to the translation along with the verb. A specific example of this is Ephesians 5:18, "...be filled with the Spirit." In the original Greek, this verse is telling us to continually be filled with the Spirit. It is not a one-time event—it is a lifelong process. This "aspect" is lost in the English translation.
With all that said, the Bible also makes it clear that the Spirit is the author of the Bible and that He will help us to understand the His Word (2 Timothy 3:16-17; John 14:26). You do not have to know Hebrew and Greek in order to understand the Bible. God's intended message for us is accurately communicated in English. You can have confidence that God can reveal the meaning of His Word to you without your knowing Greek and Hebrew.
Perhaps this is a good analogy: reading the Bible without knowing Greek and Hebrew is like watching a 20" television, while reading the Bible knowing Greek and Hebrew is like watching a 65" LED 1080p HDTV with stereo surround sound. You can understand what is going on with the 20" television, but the 65" LED HDTV with stereo surround sound gives added depth and clarity. With the help of the Holy Spirit, anyone can accurately understand the Bible in English. However, knowing Hebrew and Greek helps to better understand the nuances and richness of the biblical texts.