The NASB already is a pretty good English translation - for personal reading and basic study already very helpful. How detailed are you intending to check the Hebrew/Greek? These days online you can check the interlinear, e.g.:
Bible Hub interlinear
That's easier than manually lookup words. When you study a particular verse in detail a concordance or online tools like the one mentioned allow you to have a look at the Greek text and check what actual words were used - and how e.g. a particular Greek word is used at other places in the NT. That creates a better understanding of the meaning of such a Greek word. For detailed study it is risky to rely on just a translation - because translators have to make choices and sometimes suffer from too much interpretation.
Also free desktop software exists for that purpose:
e-Sword: Free Bible Study for the PC or
Scripture4All - Greek/Hebrew interlinear Bible software
Do you have particular themes or subjects or sections in mind or a specific interest?