Confused in Bit rate, Symbol rate, Sample rate and Data rate
The $BT$ product is linked to the single-side $-3\rm dB$ down bandwidth and the bit rate $R_b$ with the relation below: 
$$BT = \frac{f_{-\rm 3 dB}}{R_b}$$ 
Assuming you have a single-side $-3\rm dB$ bandwidth, you can extract your bit rate as:
$$R_b = \frac{f_{-\rm 3 dB}}{BT}$$ 
Also see the answer to this question. For more on GMSK see this paper $^1$ and this paper $^2$.

You have one bit per symbol, meaning for every bit you have one symbol. And their rate should be in that proportion as well. Or see it this way,
\begin{align}
\text{For} \ \ &amp;n \ \ \text{bits you have} \ \ n \ \ \text{symbols}\\
\implies \text{for} \ \ &amp;\Delta n \ \ \text{bits you have} \ \ \Delta n \ \ \text{symbols}\\
\implies \text{for} \ \ &amp;\frac{\Delta n \ \rm bits }{\Delta t} \ \ \text{you have} \ \ \frac{\Delta n \ \rm symbols}{\Delta t}
\end{align}

See the sampling rate as the rate at which you are having your samples, and this value is in $\rm Hz$, or basically
$$
\frac{\Delta n \ \rm Samples}{\Delta t}
$$ 
The $\Delta t$s above are normally given as $1 \ \rm second$. The sampling rate is the number of samples per second, also known as sampling frequency (in $\rm Hz$).

Generally speaking, your bit rate is your data rate. The answer to this question details more on this.

You can use the maths and plug in your numbers. 



$[1]$: A. Linz and A. Hendrickson, "Efficient implementation of an I-Q GMSK modulator," in IEEE Transactions on Circuits and Systems II: Analog and Digital Signal Processing, vol. 43, no. 1, pp. 14-23, Jan 1996.

$[2]$: K. Murota and K. Hirade, "GMSK Modulation for Digital Mobile Radio Telephony," in IEEE Transactions on Communications, vol. 29, no. 7, pp. 1044-1050, Jul 1981.