Receive Leads from external sources posting directly to form URL

Hi Everyone.

Overview:
I am testing Mautic and i have come across a stumbling block.
We are running test / demo instance hosted on a staging environment.
LAMP stack.

I have external systems that are used for generating leads, these systems post back responses via POST/GET URL’s to endpoints.

Usually we specify endpoints as per this example:
https://someendpointdomain.com/someAPIorForm.php?firstname=[fname]&lastname=[lname] = https://someendpointdomain.com/someAPIorForm.php?firstname=Joe&lastname=Soap
or
https://someendpointdomain.com/form001/?fname=[first_name]&lname=[last_name] = https://someendpointdomain.com/form001/?fname=Joe&lname=Soap
or
https://someendpointdomain.com/form001/?name=Joe&surname=Soap

I have gone through the manuals and forums to try and find anyone else or a reference to a simple POST/GET request to Mautic form / URL, but cannot find anything that assists me.
I have even had three separate developers take a look but none of them can figure it out.
Through some research I have found some plugins for the WordPress CMS that can POST to Mautic form, but we require posting back directly to Mautic via form or URL.

Testing different examples:
Form links:
https://someendpointdomain.com/form/submit?formId=9
https://someendpointdomain.com/form/9
For fields:
Name
Surname
Code snippet from the form:

           
          <div class="mauticform-page-wrapper mauticform-page-1" data-mautic-form-page="1">

            <div id="mauticform_test001_f_name"  class="mauticform-row mauticform-text mauticform-field-1">
                <label id="mauticform_label_test001_f_name" for="mauticform_input_test001_f_name" class="mauticform-label">Name</label>
                <input id="mauticform_input_test001_f_name" name="mauticform[f_name]" value="" placeholder="Name" class="mauticform-input" type="text" />
                <span class="mauticform-errormsg" style="display: none;"></span>
            </div>

            <div id="mauticform_test001_surname"  class="mauticform-row mauticform-text mauticform-field-2">
                <label id="mauticform_label_test001_surname" for="mauticform_input_test001_surname" class="mauticform-label">Surname</label>
                <input id="mauticform_input_test001_surname" name="mauticform[surname]" value="" placeholder="Surname" class="mauticform-input" type="text" />
                <span class="mauticform-errormsg" style="display: none;"></span>
            </div>

            <div id="mauticform_test001_submit"  class="mauticform-row mauticform-button-wrapper mauticform-field-3">
                <button type="submit" name="mauticform[submit]" id="mauticform_input_test001_submit" name="mauticform[submit]" value="" class="mauticform-button btn btn-default" value="1">Submit</button>
            </div>
            </div>
        </div>

        <input type="hidden" name="mauticform[formId]" id="mauticform_test001_id" value="9"/>
        <input type="hidden" name="mauticform[return]" id="mauticform_test001_return" value=""/>
        <input type="hidden" name="mauticform[formName]" id="mauticform_test001_name" value="test001"/>

None working examples:
https://someendpointdomain.com/form/9?mauticform[f_name]=Joe&mauticform[submit]=Soap
https://someendpointdomain.com/form/9?mauticform_input_test001_f_name=Joe&mauticform_input_test001_surname=Soap

Please if anyone could assist, or point me in the right direction, it would be very much appreciated.

Thank you.

Mautic has a full-blown API: https://developer.mautic.org/
Maybe it helps?

Thank you for the reply.
This does not help me with my request / question.
I am not a developer and have had developers look at this already ,they say it is not possible.
Hence me asking about the forms and pre-populating and posting via URL GET/POST.

Obviously the API doc shows a much better method for this, but I am unable to make it work as a none Developer. The Devs that I have asked to assist (and offered to pay and or payed) say it is not possible etc or are disinterested in making Mautic work for me, as they would rather push their own custom solutions.
I have basic experience and knowledge of setting up forms (PHP, POST and GET, CRM’s and CMS’s etc).
I thought someone might have had a similar request or knows what the missing logic in my examples is to get it working.

But again thank you for the reply, it is appreciated.

Kind Regards