Following steps should be taken to manage informal groups:
(i) Managers should ensure that informal groups should follow the rules, laid down in an organisation.
(ii) Management should use group-based approaches for decision-making and conflict handling.
(iii) Management should make an efficient use of informal groups.
(iv) Managers should assist informal groups for the betterment of organisation. 

The organising function of management helps in bringing administrative efficiency in the following ways:
(i) It leads to the elimination of overlapping and duplication of activities.
(ii) It enables people to work as a team.
(iii) It brings clarity in working relationships, thereby ensuring proper execution of work.

A functional structure is an organizational design that groups similar or related jobs together. 
1. functional structure in formed by grouping together the entire work to be done into major functional department.
2.  All deptt are report to a coordinating head
3.  These dept may further be divide into sections.
Advantages/Merits
1. Specialisation : A functional structure leads to occupational specialization since emphasis is placed on specific functions. this promotes efficiency in utilization of manpower as employee perform similar tasks within a department and are able to improve performance.
2. Efficiency : It helps in increasing managerial and operational efficiency and this results in increased profit.
3. Minimises costs : It leads to minimum duplication of efforst which results in economies of scale and thus lowers cost.
4. Better control and coordination : It promotes control and coordination within a department because of similarity in the tasks being performed.
i. Proper attention : It ensures that different functions get due attention.
5. Ease in training employees : In makes training of employees easier as the focus is only on a limited range of skills.
Disadvantages/Demerits
1. Functional empires : A functional structure places less emphasis on overall organizational objectives than the departmental objectives. Such practices may lead to functional empires wherin the importance of a particular function (or department) may be overemphasised.
2. Problems in coordination : Pursuing departmental interests at the cost of organizational interests can also hinder the interaction between two or more departments. It may lead to problems in coordination among different departments.
3. Conflict of interests : A conflict of interests may arise among departments when the interests of two or more departments are not compatible.
4. Inflexibility : It may lead to inflexibility as people with same skills and knowledge base may develop a narrow perspective and thus have difficulty in appreciating any other point of view.

For such a company, I would choose functional structure because the company has grouped the activities or jobs of similar nature into separate departments, such as manufacturing, finance, marketing and so on.
Advantages of functional structure
Functional structure has the following advantages:
(i) It leads to occupational specialisation, since emphasis is placed on specific functions and repeated performance leading to efficient functioning.
(ii) It promotes control and coordination within a department because of similarity in the tasks performed.
(iii) It leads to increased efficiency and profits.
(iv) It leads to minimal duplication of efforts, which results in economies of scale, and this lowers the cost.
(v) It makes training of employees easier as the focus is only on a limited range of skills.
(vi) It ensures that all functions get due attention. 

(a) Honesty
(b) Team spirit
(c) Unity.

Informal organisation

Formal organisation

Organising as a process is identification and division of work, departmentalisation, assigning of duties and established reporting relationship.

Louis Allen, “Organization is the process of identifying and grouping work to be performed, defining and delegating responsibility and authority and establishing relationships for the purpose of enabling people to work most effectively together in accomplishing objectives.” In the words of Allen, organization is an instrument for achieving organizational goals. The work of each and every person is defined and authority and responsibility is fixed for accomplishing the same.
Wheeler, “Internal organization is the structural framework of duties and responsibilities required of personnel in performing various functions within the company It is essentially a blue print for action resulting in a mechanism for carrying out function to achieve the goals set up by company management”. In Wheeler’s view, organization is a process of fixing duties and responsibilities of persons in an enterprise so that business goals are achieved.