Grass help needed please

Hello everyone, I’m looking for some help please regarding the grass in my garden. I have no idea at all on this so any advice would be greatly appreciated.
A lot of the grass in our garden has been taken over by weeds. What is the best way to approach to restoring the grass in these areas? Can the weeds just be pulled and seeds put back down? Is there a certain time in the year when I should do this?

Thanks in advance

 

Would you please post a wide angle shot of your lawn, so that one can see the extent of the problem?

 

It's not really a good time of year to start doing anything with grass. If you wait until spring, or whenever there's some growth, that's a better time to start sorting it.
Your lcoation and general climate are also big factors, especially when it comes to reseeding etc. and the condition of the soil also affects the growth and health of your grass. If it's compacted clay, that's always going to be different from a lighter sandier soil. There's seed to suit those different conditions too.
The aspect of the garden also affects how well grass will grow, as well as the surroundings - buildings, trees, hedges, fences etc, and also how much use/foot traffic it gets. That's where a wider pic, as suggested, and more info, will help.