Hi
New here guys so be kind

I have purchased a manual diesel 1999 voyager and have inherited a few problems i was not told about ... and may be related
Firstly while driving you can press the accelerator and nothing happens and so you have to lift off and press again to get acceleration. This does not always happen but will happen very frequently ...eg every couple of minutes.
Second ..... the car is cutting out..... some journeys this will not happen and on some it will occur 3 or 4 times. Usually on heavy breaking or coasting the engine will just stop .... the glow plug light will flash and i can turn off the ignition and re-start and it will go fine .... untill next time.
This has already nearly caused a couple of accidents
Third ... the stop lights sometimes stay on ... i have heard the switch can be adjusted but need more info.
The gear box is hard to select when cold and is knotchy in first and second ... have heard fully synthetic engine oil is better so will try this.

Any help on the main issues would be appriciated.