Suggested

canceling car improvement

I propose to make it possible to cancel the development of the car, in case the player for various reasons decided to invest development points in some other parameters.Now there is no way to cancel the save. It so happens that having invested development points in some parameter, you remain dissatisfied with the lap time. And there is no way to cancel the save.  Also, if you cancel the save, I propose to increase the number of attempts in practice to at least 10

it would create an insane struggle for research, for example you can see a good search in braking, but then they take away the points

My opinion is that putting R&D research cost budget that we can choose. It can effect design point (DP) or another functions (such as supplier efficiencies). If you have any extra fund, you can spend or you can save if you have any budget problem. 

Let's assume the current level is 100%, minimum 50% and maximum 150% (by step of 10%). Changing level may cost 1-3 gold. The function may be DP x Sqrt (R&D Budget). 

For example, if you are earning 20 DP for each race,
If you lower level to 50%, you will earn 14 DP (70%of DP (20xSqrt(0.5))) and save 50% budget
If you lower level to 100%, you will earn 20 DP (100%of DP (20xSqrt(1.0))) and no save
If you lower level to 150%, you will earn 24 DP (120%of DP (20xSqrt(1.5))) and spend 50% more budget

It can be apply other functions such as pitting time, engien/fuel/tyre supplier bonus, training or staffs efficiencies. 

I just propose adding more realism to the game. in reality, the team during training tries to find the best settings for the car.If the improvement (tuning), say the brakes, does not give the desired result, then they redo the settings and so on.Why in the game you can’t do that? Improving the brakes, you were unsatisfied. You throw off the spent improvement points and try to invest them, for example, in acceleration. I do not propose that all glasses be dropped off all the research points for all the time. And only those that I received after the race, i.e. up to 20 points. 

And what will be bad if the players start researching? Practice is for that and practice to study, find the best settings !!! Most of the time in the game there is absolutely nothing to do! Enter a couple of minutes before qualification, make standard preferences for settings and strategies. Spend half an hour in front of the screen, watching how your cars ride on the highway. All! Day is free. Boring !!!
A manager is a manager and that he must constantly think about what can be improved and what went wrong. And opportunities are needed to fix this.

In real life teams don't have DP, they invest real money and time. And then they cannot just throw away the research and recover the money already spent. This also applies to the wasted time.

In this game there's no bad improvement, so there's no point in throw away invested DP, as they cannot be the best choice for that particular track, but they're always be a step toward the ideal performance car, IMO. 
And, most important, if we can try more option in a row, then we all can quickly find the ideal development for that particular circuit, and there would no longer be that kind of challenge.

IMO, this game just needs the current problems to be fixed. This is not one of those.

I agree that they spend money and time. but if they are not satisfied with the improvement, they simply abandon it. Create a new part and test again, etc.

I think this is a good idea. In real life every team gets to set up their car to get the best possible performance out of it and that may mean adding, adjusting or taking away things if needed and as long as it falls within the regulations. So I think a 23 hour time limit after each race which allows the player to spend their design points earned (ONLY from the last race) wherever they choose and if they're not happy with their practice session they can reallocate those DP into a different attribute. Then an hour before the next race any DP spent becomes locked to that attribute and any DP left unspent becomes locked once it is used, it cannot be reallocated, much like it is now. So to compliment this idea I think an extra one or two practice runs may be needed, to make the most out of this new testing flexibility.

True but, as I've already written, there's no bad improvement in this game.

A team won't throw away anything that delivers improvement, even if the improvement isn't as big as expected. If better gains can be made elsewhere, the team will simply switch their emphasis.